Adolescence (from Latinadolescere, meaning "to grow up")[1] is a transitional stage of physical and psychologicaldevelopment that generally occurs during the period from puberty to legal adulthood (age of majority).[1][2][3] Adolescence is usually associated with the teenage years,[3][4][5][6] but its physical, psychological or cultural expressions may begin earlier and end later. For example, puberty now typically begins during preadolescence, particularly in females.[4][7][8][9][10] Physical growth (particularly in males), and cognitive development can extend into the early twenties. Thus age provides only a rough marker of adolescence, and scholars have found it difficult to agree upon a precise definition of adolescence.[7][8][11][12]

A thorough understanding of adolescence in society depends on information from various perspectives, including psychology, biology, history, sociology, education, and anthropology. Within all of these perspectives, adolescence is viewed as a transitional period between childhood and adulthood, whose cultural purpose is the preparation of children for adult roles.[13] It is a period of multiple transitions involving education, training, employment and unemployment, as well as transitions from one living circumstance to another.[14]

The end of adolescence and the beginning of adulthood varies by country and by function. Furthermore, even within a single nation state or culture there can be different ages at which an individual is considered (chronologically and legally) mature enough for society to entrust them with certain privileges and responsibilities. Such milestones include driving a vehicle, having legal sexual relations, serving in the armed forces or on a jury, purchasing and drinking alcohol, voting, entering into contracts, finishing certain levels of education, and marriage. Adolescence is usually accompanied by an increased independence allowed by the parents or legal guardians, including less supervision as compared to preadolescence.

In studying adolescent development,[15] adolescence can be defined biologically, as the physical transition marked by the onset of puberty and the termination of physical growth; cognitively, as changes in the ability to think abstractly and multi-dimensionally; or socially, as a period of preparation for adult roles. Major pubertal and biological changes include changes to the sex organs, height, weight, and muscle mass, as well as major changes in brain structure and organization. Cognitive advances encompass both increment in knowledge and in the ability to think abstractly and to reason more effectively. The study of adolescent development often involves interdisciplinary collaborations. For example, researchers in neuroscience or bio-behavioral health might focus on pubertal changes in brain structure and its effects on cognition or social relations. Sociologists interested in adolescence might focus on the acquisition of social roles (e.g., worker or romantic partner) and how this varies across cultures or social conditions.[16]Developmental psychologists might focus on changes in relations with parents and peers as a function of school structure and pubertal status.[17] Some scientists have questioned the universality of adolescence as a developmental phase, arguing that traits often considered typical of adolescents are not in fact inherent to the teenage years.

Biological development

Puberty in general

Upper body of a teenage boy. The structure has changed to resemble an adult form.

Puberty is a period of several years in which rapid physical growth and psychological changes occur, culminating in sexual maturity. The average age of onset of puberty is at 11 for girls and 12 for boys.[18][19] Every person's individual timetable for puberty is influenced primarily by heredity, although environmental factors, such as diet and exercise, also exert some influences.[20][21] These factors can also contribute to precocious and delayed puberty.[12][21]

Some of the most significant parts of pubertal development involve distinctive physiological changes in individuals' height, weight, body composition, and circulatory and respiratory systems.[22] These changes are largely influenced by hormonal activity. Hormones play an organizational role, priming the body to behave in a certain way once puberty begins,[23] and an active role, referring to changes in hormones during adolescence that trigger behavioral and physical changes.[24]

Puberty occurs through a long process and begins with a surge in hormone production, which in turn causes a number of physical changes. It is the stage of life characterized by the appearance and development of secondary sex characteristics (for example, a deeper voice and larger adam's apple in boys, and development of breasts and more curved and prominent hips in girls) and a strong shift in hormonal balance towards an adult state. This is triggered by the pituitary gland, which secretes a surge of hormonal agents into the blood stream, initiating a chain reaction to occur. The male and female gonads are subsequently activated, which puts them into a state of rapid growth and development; the triggered gonads now commence the mass production of the necessary chemicals. The testes primarily release testosterone, and the ovaries predominantly dispense estrogen. The production of these hormones increases gradually until sexual maturation is met. Some boys may develop gynecomastia due to an imbalance of sex hormones, tissue responsiveness or obesity.[25]

Facial hair in males normally appears in a specific order during puberty: The first facial hair to appear tends to grow at the corners of the upper lip, typically between 14 and 17 years of age.[26][27] It then spreads to form a moustache over the entire upper lip. This is followed by the appearance of hair on the upper part of the cheeks, and the area under the lower lip.[26] The hair eventually spreads to the sides and lower border of the chin, and the rest of the lower face to form a full beard.[26] As with most human biological processes, this specific order may vary among some individuals. Facial hair is often present in late adolescence, around ages 17 and 18, but may not appear until significantly later.[27][28] Some men do not develop full facial hair for 10 years after puberty.[27] Facial hair continues to get coarser, darker and thicker for another 2–4 years after puberty.[27]

The major landmark of puberty for males is spermarche, the first ejaculation, which occurs, on average, at age 13.[29] For females, it is menarche, the onset of menstruation, which occurs, on average, between ages 12 and 13.[20][30][31][32] The age of menarche is influenced by heredity, but a girl's diet and lifestyle contribute as well.[20] Regardless of genes, a girl must have a certain proportion of body fat to attain menarche.[20] Consequently, girls who have a high-fat diet and who are not physically active begin menstruating earlier, on average, than girls whose diet contains less fat and whose activities involve fat reducing exercise (e.g. ballet and gymnastics).[20][21] Girls who experience malnutrition or are in societies in which children are expected to perform physical labor also begin menstruating at later ages.[20]

The timing of puberty can have important psychological and social consequences. Early maturing boys are usually taller and stronger than their friends.[33] They have the advantage in capturing the attention of potential partners and in becoming hand-picked for sports. Pubescent boys often tend to have a good body image, are more confident, secure, and more independent.[34] Late maturing boys can be less confident because of poor body image when comparing themselves to already developed friends and peers. However, early puberty is not always positive for boys; early sexual maturation in boys can be accompanied by increased aggressiveness due to the surge of hormones that affect them.[34] Because they appear older than their peers, pubescent boys may face increased social pressure to conform to adult norms; society may view them as more emotionally advanced, despite the fact that their cognitive and social development may lag behind their appearance.[34] Studies have shown that early maturing boys are more likely to be sexually active and are more likely to participate in risky behaviors.[35]

For girls, early maturation can sometimes lead to increased self-consciousness, though a typical aspect in maturing females.[36] Because of their bodies' developing in advance, pubescent girls can become more insecure and dependent.[36] Consequently, girls that reach sexual maturation early are more likely than their peers to develop eating disorders (such as anorexia nervosa). Nearly half of all American high school girls' diets are to lose weight.[36] In addition, girls may have to deal with sexual advances from older boys before they are emotionally and mentally mature.[37] In addition to having earlier sexual experiences and more unwanted pregnancies than late maturing girls, early maturing girls are more exposed to alcohol and drug abuse.[38] Those who have had such experiences tend to perform not as well in school as their "inexperienced" peers.[39]

Girls have usually reached full physical development around ages 15–17,[3][19][40] while boys usually complete puberty around ages 16–17.[19][40][41] Any increase in height beyond the post-pubertal age is uncommon. Girls attain reproductive maturity about four years after the first physical changes of puberty appear.[3] In contrast, boys accelerate more slowly but continue to grow for about six years after the first visible pubertal changes.[34][41]

Approximate outline of development periods in child and teenager development. Adolescence is marked in red at top right.

Growth spurt

The adolescent growth spurt is a rapid increase in the individual's height and weight during puberty resulting from the simultaneous release of growth hormones, thyroid hormones, and androgens.[42] Males experience their growth spurt about two years later, on average, than females. During their peak height velocity (the time of most rapid growth), adolescents grow at a growth rate nearly identical to that of a toddler—about 4 inches (10.3 cm) a year for males and 3.5 inches (9 cm) for females.[43] In addition to changes in height, adolescents also experience a significant increase in weight (Marshall, 1978). The weight gained during adolescence constitutes nearly half of one's adult body weight.[43] Teenage and early adult males may continue to gain natural muscle growth even after puberty.[34]

The accelerated growth in different body parts happens at different times, but for all adolescents it has a fairly regular sequence. The first places to grow are the extremities—the head, hands and feet—followed by the arms and legs, then the torso and shoulders.[44] This non-uniform growth is one reason why an adolescent body may seem out of proportion.

During puberty, bones become harder and more brittle. At the conclusion of puberty, the ends of the long bones close during the process called epiphysis. There can be ethnic differences in these skeletal changes. For example, in the United States of America, bone density increases significantly more among black than white adolescents, which might account for decreased likelihood of black women developing osteoporosis and having fewer bone fractures there.[45]

Another set of significant physical changes during puberty happen in bodily distribution of fat and muscle. This process is different for females and males. Before puberty, there are nearly no sex differences in fat and muscle distribution; during puberty, boys grow muscle much faster than girls, although both sexes experience rapid muscle development. In contrast, though both sexes experience an increase in body fat, the increase is much more significant for girls. Frequently, the increase in fat for girls happens in their years just before puberty. The ratio between muscle and fat among post-pubertal boys is around three to one, while for girls it is about five to four. This may help explain sex differences in athletic performance.[46]

Pubertal development also affects circulatory and respiratory systems as an adolescents' heart and lungs increase in both size and capacity. These changes lead to increased strength and tolerance for exercise. Sex differences are apparent as males tend to develop "larger hearts and lungs, higher systolic blood pressure, a lower resting heart rate, a greater capacity for carrying oxygen to the blood, a greater power for neutralizing the chemical products of muscular exercise, higher blood hemoglobin and more red blood cells".[47]

Despite some genetic sex differences, environmental factors play a large role in biological changes during adolescence. For example, girls tend to reduce their physical activity in preadolescence[48][49] and may receive inadequate nutrition from diets that often lack important nutrients, such as iron.[50] These environmental influences in turn affect female physical development.

Reproduction-related changes

Primary sex characteristics are those directly related to the sex organs. In males, the first stages of puberty involve growth of the testes and scrotum, followed by growth of the penis.[51] At the time that the penis develops, the seminal vesicles, the prostate, and the bulbourethral gland also enlarge and develop. The first ejaculation of seminal fluid generally occurs about one year after the beginning of accelerated penis growth, although this is often determined culturally rather than biologically, since for many boys first ejaculation occurs as a result of masturbation.[44] Boys are generally fertile before they have an adult appearance.[42]

In females, changes in the primary sex characteristics involve growth of the uterus, vagina, and other aspects of the reproductive system. Menarche, the beginning of menstruation, is a relatively late development which follows a long series of hormonal changes.[52] Generally, a girl is not fully fertile until several years after menarche, as regular ovulation follows menarche by about two years.[53] Unlike males, therefore, females usually appear physically mature before they are capable of becoming pregnant.

Changes in secondary sex characteristics include every change that is not directly related to sexual reproduction. In males, these changes involve appearance of pubic, facial, and body hair, deepening of the voice, roughening of the skin around the upper arms and thighs, and increased development of the sweat glands. In females, secondary sex changes involve elevation of the breasts, widening of the hips, development of pubic and underarm hair, widening of the areolae, and elevation of the nipples.[54] The changes in secondary sex characteristics that take place during puberty are often referred to in terms of five Tanner stages,[55] named after the British pediatrician who devised the categorization system.

Changes in the brain

The human brain is not fully developed by the time a person reaches puberty. Between the ages of 10 and 25, the brain undergoes changes that have important implications for behavior (see Cognitive development below). The brain reaches 90% of its adult size by the time a person is six years of age.[56] Thus, the brain does not grow in size much during adolescence. However, the creases in the brain continue to become more complex until the late teens. The biggest changes in the folds of the brain during this time occur in the parts of the cortex that process cognitive and emotional information.[56]

Over the course of adolescence, the amount of white matter in the brain increases linearly, while the amount of grey matter in the brain follows an inverted-U pattern.[57] Through a process called synaptic pruning, unnecessary neuronal connections in the brain are eliminated and the amount of grey matter is pared down. However, this does not mean that the brain loses functionality; rather, it becomes more efficient due to increased myelination (insulation of axons) and the reduction of unused pathways.[58]

The first areas of the brain to be pruned are those involving primary functions, such as motor and sensory areas. The areas of the brain involved in more complex processes lose matter later in development. These include the lateral and prefrontal cortices, among other regions.[59] Some of the most developmentally significant changes in the brain occur in the prefrontal cortex, which is involved in decision making and cognitive control, as well as other higher cognitive functions. During adolescence, myelination and synaptic pruning in the prefrontal cortex increases, improving the efficiency of information processing, and neural connections between the prefrontal cortex and other regions of the brain are strengthened.[60] This leads to better evaluation of risks and rewards, as well as improved control over impulses. Specifically, developments in the dorsolateral prefrontal cortex are important for controlling impulses and planning ahead, while development in the ventromedial prefrontal cortex is important for decision making. Changes in the orbitofrontal cortex are important for evaluating rewards and risks.

Three neurotransmitters that play important roles in adolescent brain development are glutamate, dopamine and serotonin. Glutamate is an excitatory neurotransmitter. During the synaptic pruning that occurs during adolescence, most of the neural connections that are pruned contain receptors for glutamate or other excitatory neurotransmitters.[61] Because of this, by early adulthood the synaptic balance in the brain is more inhibitory than excitatory.

Dopamine is associated with pleasure and attuning to the environment during decision-making. During adolescence, dopamine levels in the limbic system increase and input of dopamine to the prefrontal cortex increases.[62] The balance of excitatory to inhibitory neurotransmitters and increased dopamine activity in adolescence may have implications for adolescent risk-taking and vulnerability to boredom (see Cognitive development below).

Serotonin is a neuromodulator involved in regulation of mood and behavior. Development in the limbic system plays an important role in determining rewards and punishments and processing emotional experience and social information. Changes in the levels of the neurotransmitters dopamine and serotonin in the limbic system make adolescents more emotional and more responsive to rewards and stress. The corresponding increase in emotional variability also can increase adolescents' vulnerability. The effect of serotonin is not limited to the limbic system: Several serotonin receptors have their gene expression change dramatically during adolescence, particularly in the human frontal and prefrontal cortex .[63]

Cognitive development

Adolescence is also a time for rapid cognitive development.[64]Piaget describes adolescence as the stage of life in which the individual's thoughts start taking more of an abstract form and the egocentric thoughts decrease. This allows the individual to think and reason in a wider perspective.[65] A combination of behavioural and fMRI studies have demonstrated development of executive functions, that is, cognitive skills that enable the control and coordination of thoughts and behaviour, which are generally associated with the prefrontal cortex.[66] The thoughts, ideas and concepts developed at this period of life greatly influence one's future life, playing a major role in character and personality formation.[67]

Biological changes in brain structure and connectivity within the brain interact with increased experience, knowledge, and changing social demands to produce rapid cognitive growth (see Changes in the brain above). The age at which particular changes take place varies between individuals, but the changes discussed below begin at puberty or shortly after that and some skills continue to develop as the adolescent ages. The dual systems model proposes a maturational imbalance between development of the socioemotional system and cognitive control systems in the brain that contribute to impulsivity and other behaviors characteristic of adolescence.[68]

Theoretical perspectives

There are at least two major approaches to understanding cognitive change during adolescence. One is the constructivist view of cognitive development. Based on the work of Piaget, it takes a quantitative, state-theory approach, hypothesizing that adolescents' cognitive improvement is relatively sudden and drastic. The second is the information-processing perspective, which derives from the study of artificial intelligence and attempts to explain cognitive development in terms of the growth of specific components of the thinking process.

Improvements in cognitive ability

By the time individuals have reached age 15 or so, their basic thinking abilities are comparable to those of adults. These improvements occur in five areas during adolescence:

Attention. Improvements are seen in selective attention, the process by which one focuses on one stimulus while tuning out another. Divided attention, the ability to pay attention to two or more stimuli at the same time, also improves.[69][70]

Processing speed. Adolescents think more quickly than children. Processing speed improves sharply between age five and middle adolescence; it then begins to level off at age 15 and does not appear to change between late adolescence and adulthood.[72]

Organization. Adolescents are more aware of their thought processes and can use mnemonic devices and other strategies to think more efficiently.[73]

Studies since 2005 indicate that the brain is not fully formed until the early twenties.[74]

Hypothetical and abstract thinking

Adolescents' thinking is less bound to concrete events than that of children: they can contemplate possibilities outside the realm of what currently exists. One manifestation of the adolescent's increased facility with thinking about possibilities is the improvement of skill in deductive reasoning, which leads to the development of hypothetical thinking. This provides the ability to plan ahead, see the future consequences of an action and to provide alternative explanations of events. It also makes adolescents more skilled debaters, as they can reason against a friend's or parent's assumptions. Adolescents also develop a more sophisticated understanding of probability.

The appearance of more systematic, abstract thinking is another notable aspect of cognitive development during adolescence. For example, adolescents find it easier than children to comprehend the sorts of higher-order abstract logic inherent in puns, proverbs, metaphors, and analogies. Their increased facility permits them to appreciate the ways in which language can be used to convey multiple messages, such as satire, metaphor, and sarcasm. (Children younger than age nine often cannot comprehend sarcasm at all.)[75] This also permits the application of advanced reasoning and logical processes to social and ideological matters such as interpersonal relationships, politics, philosophy, religion, morality, friendship, faith, fairness, and honesty.

Metacognition

A third gain in cognitive ability involves thinking about thinking itself, a process referred to as metacognition. It often involves monitoring one's own cognitive activity during the thinking process. Adolescents' improvements in knowledge of their own thinking patterns lead to better self-control and more effective studying. It is also relevant in social cognition, resulting in increased introspection, self-consciousness, and intellectualization (in the sense of thought about one's own thoughts, rather than the Freudian definition as a defense mechanism). Adolescents are much better able than children to understand that people do not have complete control over their mental activity. Being able to introspect may lead to two forms of adolescent egocentrism, which results in two distinct problems in thinking: the imaginary audience and the personal fable. These likely peak at age fifteen, along with self-consciousness in general.[76]

Related to metacognition and abstract thought, perspective-taking involves a more sophisticated theory of mind.[77] Adolescents reach a stage of social perspective-taking in which they can understand how the thoughts or actions of one person can influence those of another person, even if they personally are not involved.[78]

Relativistic thinking

Compared to children, adolescents are more likely to question others' assertions, and less likely to accept facts as absolute truths. Through experience outside the family circle, they learn that rules they were taught as absolute are in fact relativistic. They begin to differentiate between rules instituted out of common sense—not touching a hot stove—and those that are based on culturally-relative standards (codes of etiquette, not dating until a certain age), a delineation that younger children do not make. This can lead to a period of questioning authority in all domains.[79]

Wisdom

Wisdom, or the capacity for insight and judgment that is developed through experience,[80] increases between the ages of fourteen and twenty-five, then levels off. Thus, it is during the adolescence-adulthood transition that individuals acquire the type of wisdom that is associated with age. Wisdom is not the same as intelligence: adolescents do not improve substantially on IQ tests since their scores are relative to others in their same age group, and relative standing usually does not change—everyone matures at approximately the same rate in this way.

Risk-taking

Because most injuries sustained by adolescents are related to risky behavior (car crashes, alcohol, unprotected sex), a great deal of research has been done on the cognitive and emotional processes underlying adolescent risk-taking. In addressing this question, it is important to distinguish whether adolescents are more likely to engage in risky behaviors (prevalence), whether they make risk-related decisions similarly or differently than adults (cognitive processing perspective), or whether they use the same processes but value different things and thus arrive at different conclusions. The behavioral decision-making theory proposes that adolescents and adults both weigh the potential rewards and consequences of an action. However, research has shown that adolescents seem to give more weight to rewards, particularly social rewards, than do adults.[81]

Research seems to favor the hypothesis that adolescents and adults think about risk in similar ways, but hold different values and thus come to different conclusions. Some have argued that there may be evolutionary benefits to an increased propensity for risk-taking in adolescence. For example, without a willingness to take risks, teenagers would not have the motivation or confidence necessary to leave their family of origin. In addition, from a population perspective, there is an advantage to having a group of individuals willing to take more risks and try new methods, counterbalancing the more conservative elements more typical of the received knowledge held by older adults. Risktaking may also have reproductive advantages: adolescents have a newfound priority in sexual attraction and dating, and risk-taking is required to impress potential mates. Research also indicates that baseline sensation seeking may affect risk-taking behavior throughout the lifespan.[82][83]

Given the potential consequences, engaging in sexual behavior is somewhat risky, particularly for adolescents. Having unprotected sex, using poor birth control methods (e.g. withdrawal), having multiple sexual partners, and poor communication are some aspects of sexual behavior that increase individual and/or social risk. Some qualities of adolescents' lives that are often correlated with risky sexual behavior include higher rates of experienced abuse, lower rates of parental support and monitoring.[84]

Inhibition

Related to their increased tendency for risk-taking, adolescents show impaired behavioral inhibition, including deficits in extinction learning.[85] This has important implications for engaging in risky behavior such as unsafe sex or illicit drug use, as adolescents are less likely to inhibit actions that may have negative outcomes in the future.[86] This phenomenon also has consequences for behavioral treatments based on the principle of extinction, such as cue exposure therapy for anxiety or drug addiction.[87][88] It has been suggested that impaired inhibition, specifically extinction, may help to explain adolescent propensity to relapse to drug-seeking even following behavioral treatment for addiction.[89]

Psychological development

G. Stanley Hall

The formal study of adolescent psychology began with the publication of G. Stanley Hall's "Adolescence in 1904." Hall, who was the first president of the American Psychological Association, viewed adolescence primarily as a time of internal turmoil and upheaval (sturm und drang). This understanding of youth was based on two then new ways of understanding human behavior: Darwin's evolutionary theory and Freud's psychodynamic theory. He believed that adolescence was a representation of our human ancestors' phylogenetic shift from being primitive to being civilized. Hall's assertions stood relatively uncontested until the 1950s when psychologists such as Erik Erikson and Anna Freud started to formulate their theories about adolescence. Freud believed that the psychological disturbances associated with youth were biologically based and culturally universal while Erikson focused on the dichotomy between identity formation and role fulfillment.[90] Even with their different theories, these three psychologists agreed that adolescence was inherently a time of disturbance and psychological confusion. The less turbulent aspects of adolescence, such as peer relations and cultural influence, were left largely ignored until the 1980s. From the '50s until the '80s, the focus of the field was mainly on describing patterns of behavior as opposed to explaining them.[90]

Jean Macfarlane founded the University of California, Berkeley's Institute of Human Development, formerly called the Institute of Child Welfare, in 1927.[91] The Institute was instrumental in initiating studies of healthy development, in contrast to previous work that had been dominated by theories based on pathological personalities.[91] The studies looked at human development during the Great Depression and World War II, unique historical circumstances under which a generation of children grew up. The Oakland Growth Study, initiated by Harold Jones and Herbert Stolz in 1931, aimed to study the physical, intellectual, and social development of children in the Oakland area. Data collection began in 1932 and continued until 1981, allowing the researchers to gather longitudinal data on the individuals that extended past adolescence into adulthood. Jean Macfarlane launched the Berkeley Guidance Study, which examined the development of children in terms of their socioeconomic and family backgrounds.[92] These studies provided the background for Glen Elder in the 1960s, to propose a life-course perspective of adolescent development. Elder formulated several descriptive principles of adolescent development. The principle of historical time and place states that an individual's development is shaped by the period and location in which they grow up. The principle of the importance of timing in one's life refers to the different impact that life events have on development based on when in one's life they occur. The idea of linked lives states that one's development is shaped by the interconnected network of relationships of which one is a part; and the principle of human agency asserts that one's life course is constructed via the choices and actions of an individual within the context of their historical period and social network.[93]

In 1984, the Society for Research on Adolescence (SRA) became the first official organization dedicated to the study of adolescent psychology. Some of the issues first addressed by this group include: the nature versus nurture debate as it pertains to adolescence; understanding the interactions between adolescents and their environment; and considering culture, social groups, and historical context when interpreting adolescent behavior.[90]

Social development

Identity development

Identity development is a stage in the adolescent life cycle.[95] For most, the search for identity begins in the adolescent years. During these years, adolescents are more open to 'trying on' different behaviours and appearances to discover who they are.[96] In an attempt to find their identity and discover who they are, adolescents are liklely to cycle through a number of identities to find one that suits them best. Developing and maintaining identity (in adolescent years) is a difficult task due to multiple factors such as family life, environment, and social status.[95] Empirical studies suggest that this process might be more accurately described as identity development, rather than formation, but confirms a normative process of change in both content and structure of one's thoughts about the self.[97] The two main aspects of identity development are self-clarity and self-esteem.[96] Since choices made during adolescent years can influence later life, high levels of self-awareness and self-control during mid-adolescence will lead to better decisions during the transition to adulthood.[citation needed] Researchers have used three general approaches to understanding identity development: self-concept, sense of identity, and self-esteem. The years of adolescence create a more conscientious group of young adults. Adolescents pay close attention and give more time and effort to their appearance as their body goes through changes. Unlike children, teens put forth an effort to look presentable (1991).[4] The environment in which an adolescent grows up also plays an important role in their identity development. Studies done by the American Psychological Association have shown that adolescents with a less privileged upbringing have a more difficult time developing their identity.[98]

Self-concept

The idea of self-concept is known as the ability of a person to have opinions and beliefs that are defined confidently, consistent and stable.[99] Early in adolescence, cognitive developments result in greater self-awareness, greater awareness of others and their thoughts and judgments, the ability to think about abstract, future possibilities, and the ability to consider multiple possibilities at once. As a result, adolescents experience a significant shift from the simple, concrete, and global self-descriptions typical of young children; as children, they defined themselves by physical traits whereas as adolescents, they define themselves based on their values, thoughts, and opinions.[100]

Adolescents can conceptualize multiple "possible selves" that they could become[101] and long-term possibilities and consequences of their choices.[102] Exploring these possibilities may result in abrupt changes in self-presentation as the adolescent chooses or rejects qualities and behaviors, trying to guide the actual self toward the ideal self (who the adolescent wishes to be) and away from the feared self (who the adolescent does not want to be). For many, these distinctions are uncomfortable, but they also appear to motivate achievement through behavior consistent with the ideal and distinct from the feared possible selves.[101][103]

Further distinctions in self-concept, called "differentiation," occur as the adolescent recognizes the contextual influences on their own behavior and the perceptions of others, and begin to qualify their traits when asked to describe themselves.[104] Differentiation appears fully developed by mid-adolescence.[105] Peaking in the 7th-9th grades, the personality traits adolescents use to describe themselves refer to specific contexts, and therefore may contradict one another. The recognition of inconsistent content in the self-concept is a common source of distress in these years (see Cognitive dissonance),[106] but this distress may benefit adolescents by encouraging structural development.

Sense of identity

Egocentrism in adolescents forms a self-conscious desire to feel important in their peer groups and enjoy social acceptance.[107] Unlike the conflicting aspects of self-concept, identity represents a coherent sense of self stable across circumstances and including past experiences and future goals. Everyone has a self-concept, whereas Erik Erikson argued that not everyone fully achieves identity. Erikson's theory of stages of development includes the identity crisis in which adolescents must explore different possibilities and integrate different parts of themselves before committing to their beliefs. He described the resolution of this process as a stage of "identity achievement" but also stressed that the identity challenge "is never fully resolved once and for all at one point in time".[108] Adolescents begin by defining themselves based on their crowd membership. "Clothes help teens explore new identities, separate from parents, and bond with peers." Fashion has played a major role when it comes to teenagers "finding their selves"; Fashion is always evolving, which corresponds with the evolution of change in the personality of teenagers.[109] Adolescents attempt to define their identity by consciously styling themselves in different manners to find what best suits them. Trial and error in matching both their perceived image and the image others respond to and see, allows for the adolescent to grasp an understanding of who they are[110] Just as fashion is evolving to influence adolescents so is the media. "Modern life takes place amidst a never-ending barrage of flesh on screens, pages, and billboards."[111] This barrage consciously or subconsciously registers into the mind causing issues with self-image a factor that contributes to an adolescence sense of identity. Researcher James Marcia developed the current method for testing an individual's progress along these stages.[112][113] His questions are divided into three categories: occupation, ideology, and interpersonal relationships. Answers are scored based on extent to which the individual has explored and the degree to which he has made commitments. The result is classification of the individual into a) identity diffusion in which all children begin, b) Identity Foreclosure in which commitments are made without the exploration of alternatives, c) Moratorium, or the process of exploration, or d) Identity Achievement in which Moratorium has occurred and resulted in commitments.[114]

Research since reveals self-examination beginning early in adolescence, but identity achievement rarely occurring before age 18.[115] The freshman year of college influences identity development significantly, but may actually prolong psychosocial moratorium by encouraging reexamination of previous commitments and further exploration of alternate possibilities without encouraging resolution.[116] For the most part, evidence has supported Erikson's stages: each correlates with the personality traits he originally predicted.[114] Studies also confirm the impermanence of the stages; there is no final endpoint in identity development.[117]

Environment and identity

An adolescent's environment plays a huge role in their identity development.[98] While most adolescent studies are conducted on white, middle class children, studies show that the more privileged upbringing people have, the more successfully they develop their identity.[98] The forming of an adolescent's identity is a crucial time in their life. It has been recently found that demographic patterns suggest that the transition to adulthood is now occurring over a longer span of years than was the case during the middle of the 20th century. Accordingly, youth, a period that spans late adolescence and early adulthood, has become a more prominent stage of the life course. This therefore has caused various factors to become important during this development.[118] So many factors contribute to the developing social identity of an adolescent from commitment, to coping devices,[119] to social media. All of these factors are affected by the environment an adolescent grows up in. A child from a more privileged upbringing is exposed to more opportunities and better situations in general. An adolescent from an inner city or a crime-driven neighborhood is more likely to be exposed to an environment that can be detrimental to their development. Adolescence is a sensitive period in the development process, and exposure to the wrong things at that time can have a major effect on future decisions. While children that grow up in nice suburban communities are not exposed to bad environments they are more likely to participate in activities that can benefit their identity and contribute to a more successful identity development.[98]

Sexual orientation and identity

Sexual orientation has been defined as "an erotic inclination toward people of one or more genders, most often described as sexual or erotic attractions".[120] In recent years, psychologists have sought to understand how sexual orientation develops during adolescence. Some theorists believe that there are many different possible developmental paths one could take, and that the specific path an individual follows may be determined by their sex, orientation, and when they reached the onset of puberty.[120]

In 1989, Troiden proposed a four-stage model for the development of homosexual sexual identity.[121] The first stage, known as sensitization, usually starts in childhood, and is marked by the child's becoming aware of same-sex attractions. The second stage, identity confusion, tends to occur a few years later. In this stage, the youth is overwhelmed by feelings of inner turmoil regarding their sexual orientation, and begins to engage sexual experiences with same-sex partners. In the third stage of identity assumption, which usually takes place a few years after the adolescent has left home, adolescents begin to come out to their family and close friends, and assumes a self-definition as gay, lesbian, or bisexual.[122] In the final stage, known as commitment, the young adult adopts their sexual identity as a lifestyle. Therefore, this model estimates that the process of coming out begins in childhood, and continues through the early to mid 20s. This model has been contested, and alternate ideas have been explored in recent years.

In terms of sexual identity, adolescence is when most gay/lesbian and transgender adolescents begin to recognize and make sense of their feelings. Many adolescents may choose to come out during this period of their life once an identity has been formed; many others may go through a period of questioning or denial, which can include experimentation with both homosexual and heterosexual experiences.[123] A study of 194 lesbian, gay, and bisexual youths under the age of 21 found that having an awareness of one's sexual orientation occurred, on average, around age 10, but the process of coming out to peers and adults occurred around age 16 and 17, respectively.[124] Coming to terms with and creating a positive LGBT identity can be difficult for some youth for a variety of reasons. Peer pressure is a large factor when youth who are questioning their sexuality or gender identity are surrounded by heteronormative peers and can cause great distress due to a feeling of being different from everyone else. While coming out can also foster better psychological adjustment, the risks associated are real. Indeed, coming out in the midst of a heteronormative peer environment often comes with the risk of ostracism, hurtful jokes, and even violence.[123] Because of this, statistically the suicide rate amongst LGBT adolescents is up to four times higher than that of their heterosexual peers due to bullying and rejection from peers or family members.[125]

Self-esteem

The final major aspect of identity formation is self-esteem. Self-esteem is defined as one's thoughts and feelings about one's self-concept and identity.[126] Most theories on self-esteem state that there is a grand desire, across all genders and ages, to maintain, protect and enhance their self-esteem.[99] Contrary to popular belief, there is no empirical evidence for a significant drop in self-esteem over the course of adolescence.[127] "Barometric self-esteem" fluctuates rapidly and can cause severe distress and anxiety, but baseline self-esteem remains highly stable across adolescence.[128] The validity of global self-esteem scales has been questioned, and many suggest that more specific scales might reveal more about the adolescent experience.[129] Girls are most likely to enjoy high self-esteem when engaged in supportive relationships with friends, the most important function of friendship to them is having someone who can provide social and moral support. When they fail to win friends' approval or couldn't find someone with whom to share common activities and common interests, in these cases, girls suffer from low self-esteem. In contrast, boys are more concerned with establishing and asserting their independence and defining their relation to authority.[130] As such, they are more likely to derive high self-esteem from their ability to successfully influence their friends; on the other hand, the lack of romantic competence, for example, failure to win or maintain the affection of the opposite or same-sex (depending on sexual orientation), is the major contributor to low self-esteem in adolescent boys. Due to the fact that both men and women happen to have a low self-esteem after ending a romantic relationship, they are prone to other symptoms that is caused by this state. Depression and hopelessness are only two of the various symptoms and it is said that women are twice as likely to experience depression and men are three to four times more likely to commit suicide (Mearns, 1991; Ustun & Sartorius, 1995).[131]

Relationships

In general

The relationships adolescents have with their peers, family, and members of their social sphere play a vital role in the social development of an adolescent. As an adolescent's social sphere develops rapidly as they distinguish the differences between friends and acquaintances, they often become heavily emotionally invested in friends.[132] This is not harmful; however, if these friends expose an individual to potentially harmful situations, this is an aspect of peer pressure. Adolescence is a critical period in social development because adolescents can be easily influenced by the people they develop close relationships with. This is the first time individuals can truly make their own decisions, which also makes this a sensitive period. Relationships are vital in the social development of an adolescent due to the extreme influence peers can have over an individual. These relationships become significant because they begin to help the adolescent understand the concept of personalities, how they form and why a person has that specific type of personality. "The use of psychological comparisons could serve both as an index of the growth of an implicit personality theory and as a component process accounting for its creation. In other words, by comparing one person's personality characteristics to another's, we would be setting up the framework for creating a general theory of personality (and, ... such a theory would serve as a useful framework for coming to understand specific persons)."[133] This can be likened to the use of social comparison in developing one's identity and self-concept, which includes ones personality, and underscores the importance of communication, and thus relationships, in one's development. In social comparison we use reference groups, with respect to both psychological and identity development.[134] These reference groups are the peers of adolescents. This means that who the teen chooses/accepts as their friends and who they communicate with on a frequent basis often makes up their reference groups and can therefore have a huge impact on who they become. Research shows that relationships have the largest affect over the social development of an individual.

Family

Adolescence marks a rapid change in one's role within a family. Young children tend to assert themselves forcefully, but are unable to demonstrate much influence over family decisions until early adolescence,[135] when they are increasingly viewed by parents as equals. The adolescent faces the task of increasing independence while preserving a caring relationship with his or her parents.[110] When children go through puberty, there is often a significant increase in parent–child conflict and a less cohesive familial bond. Arguments often concern minor issues of control, such as curfew, acceptable clothing, and the adolescent's right to privacy,[136][137] which adolescents may have previously viewed as issues over which their parents had complete authority.[138] Parent-adolescent disagreement also increases as friends demonstrate a greater impact on one another, new influences on the adolescent that may be in opposition to parents' values. Social media has also played an increasing role in adolescent and parent disagreements.[139] While parents never had to worry about the threats of social media in the past, it has become a dangerous place for children. While adolescents strive for their freedoms, the unknowns to parents of what their child is doing on social media sites is a challenging subject, due to the increasing amount of predators on social media sites. Many parents have very little knowledge of social networking sites in the first place and this further increases their mistrust. An important challenge for the parent–adolescent relationship is to understand how to enhance the opportunities of online communication while managing its risks.[99] Although conflicts between children and parents increase during adolescence, these are just relatively minor issues. Regarding their important life issues, most adolescents still share the same attitudes and values as their parents.[140]

During childhood, siblings are a source of conflict and frustration as well as a support system.[141] Adolescence may affect this relationship differently, depending on sibling gender. In same-sex sibling pairs, intimacy increases during early adolescence, then remains stable. Mixed-sex siblings pairs act differently; siblings drift apart during early adolescent years, but experience an increase in intimacy starting at middle adolescence.[142] Sibling interactions are children's first relational experiences, the ones that shape their social and self-understanding for life.[143] Sustaining positive sibling relations can assist adolescents in a number of ways. Siblings are able to act as peers, and may increase one another's sociability and feelings of self-worth. Older siblings can give guidance to younger siblings, although the impact of this can be either positive or negative depending on the activity of the older sibling.

A potential important influence on adolescence is change of the family dynamic, specifically divorce. With the divorce rate up to about 50%,[144] divorce is common and adds to the already great amount of change in adolescence. Custody disputes soon after a divorce often reflect a playing out of control battles and ambivalence between parents. Divorce usually results in less contact between the adolescent and their noncustodial parent.[145] In extreme cases of instability and abuse in homes, divorce can have a positive effect on families due to less conflict in the home. However, most research suggests a negative effect on adolescence as well as later development. A recent study found that, compared with peers who grow up in stable post-divorce families, children of divorce who experience additional family transitions during late adolescence, make less progress in their math and social studies performance over time.[146] Another recent study put forth a new theory entitled the adolescent epistemological trauma theory,[147] which posited that traumatic life events such as parental divorce during the formative period of late adolescence portend lifelong effects on adult conflict behavior that can be mitigated by effective behavioral assessment and training.[147] A parental divorce during childhood or adolescence continues to have a negative effect when a person is in his or her twenties and early thirties. These negative effects include romantic relationships and conflict style, meaning as adults, they are more likely to use the styles of avoidance and competing in conflict management.[148]

Despite changing family roles during adolescence, the home environment and parents are still important for the behaviors and choices of adolescents.[149] Adolescents who have a good relationship with their parents are less likely to engage in various risk behaviors, such as smoking, drinking, fighting, and/or unprotected sexual intercourse.[149] In addition, parents influence the education of adolescence. A study conducted by Adalbjarnardottir and Blondal (2009) showed that adolescents at the age of 14 who identify their parents as authoritative figures are more likely to complete secondary education by the age of 22—as support and encouragement from an authoritative parent motivates the adolescence to complete schooling to avoid disappointing that parent.[150]

Peers

Top: Students of a U.S. university do an outdoor class, where they discuss topics while walking. Above: Students study in a U.S. university library, using books and a laptops.

Peer groups are essential to social and general development. Communication with peers increases significantly during adolescence and peer relationships become more intense than in other stages[151] and more influential to the teen, affecting both the decisions and choices being made.[152] High quality friendships may enhance children's development regardless of the characteristics of those friends. As children begin to bond with various people and create friendships, it later helps them when they are adolescent and sets up the framework for adolescence and peer groups.[153]Peer groups are especially important during adolescence, a period of development characterized by a dramatic increase in time spent with peers[154] and a decrease in adult supervision.[155] Adolescents also associate with friends of the opposite sex much more than in childhood[156] and tend to identify with larger groups of peers based on shared characteristics.[157] It is also common for adolescents to use friends as coping devices in different situations.[158] A three-factor structure of dealing with friends including avoidance, mastery, and nonchalance has shown that adolescents use friends as coping devices with social stresses.

Communication within peer groups allows adolescents to explore their feelings and identity as well as develop and evaluate their social skills. Peer groups offer members the opportunity to develop social skills such as empathy, sharing, and leadership. Adolescents choose peer groups based on characteristics similarly found in themselves.[110] By utilizing these relationships, adolescents become more accepting of who they are becoming. Group norms and values are incorporated into an adolescent's own self-concept.[152] Through developing new communication skills and reflecting upon those of their peers, as well as self-opinions and values, an adolescent can share and express emotions and other concerns without fear of rejection or judgment. Peer groups can have positive influences on an individual, such as on academic motivation and performance. However, while peers may facilitate social development for one another they may also hinder it. Peers can have negative influences, such as encouraging experimentation with drugs, drinking, vandalism, and stealing through peer pressure.[159] Susceptibility to peer pressure increases during early adolescence, peaks around age 14, and declines thereafter.[160] Further evidence of peers hindering social development has been found in Spanish teenagers, where emotional (rather than solution-based) reactions to problems and emotional instability have been linked with physical aggression against peers.[161] Both physical and relational aggression are linked to a vast number of enduring psychological difficulties, especially depression, as is social rejection.[162] Because of this, bullied adolescents often develop problems that lead to further victimization.[163] Bullied adolescents are more likely to both continue to be bullied and to bully others in the future.[164] However, this relationship is less stable in cases of cyberbullying, a relatively new issue among adolescents.

Adolescents tend to associate with "cliques" on a small scale and "crowds" on a larger scale. During early adolescence, adolescents often associate in cliques, exclusive, single-sex groups of peers with whom they are particularly close. Despite the common[according to whom?] notion that cliques are an inherently negative influence, they may help adolescents become socially acclimated and form a stronger sense of identity. Within a clique of highly athletic male-peers, for example, the clique may create a stronger sense of fidelity and competition. Cliques also have become somewhat a "collective parent", i.e. telling the adolescents what to do and not to do.[165] Towards late adolescence, cliques often merge into mixed-sex groups as teenagers begin romantically engaging with one another.[166] These small friend groups then break down further as socialization becomes more couple-oriented. On a larger scale, adolescents often associate with crowds, groups of individuals who share a common interest or activity. Often, crowd identities may be the basis for stereotyping young people, such as jocks or nerds. In large, multi-ethnic high schools, there are often ethnically determined crowds.[167] While crowds are very influential during early and middle adolescence, they lose salience during high school as students identify more individually.[168]

An important aspect of communication is the channel used. Channel, in this respect, refers to the form of communication, be it face-to-face, email, text message, phone or other. Teens are heavy users of newer forms of communication such as text message and social-networking websites such as Facebook, especially when communicating with peers.[169] Adolescents use online technology to experiment with emerging identities and to broaden their peer groups, such as increasing the amount of friends acquired on Facebook and other social media sites.[152] Some adolescents use these newer channels to enhance relationships with peers however there can be negative uses as well such as cyberbullying, as mentioned previously, and negative impacts on the family.[169]

Romance and sexual activity

Romantic relationships tend to increase in prevalence throughout adolescence. By age 15, 53% of adolescents have had a romantic relationship that lasted at least one month over the course of the previous 18 months.[170] In a 2008 study conducted by YouGov for Channel 4, 20% of 14−17-year-olds surveyed revealed that they had their first sexual experience at 13 or under in the United Kingdom.[171] A 2002 American study found that those aged 15–44 reported that the average age of first sexual intercourse was 17.0 for males and 17.3 for females.[172] The typical duration of relationships increases throughout the teenage years as well. This constant increase in the likelihood of a long-term relationship can be explained by sexual maturation and the development of cognitive skills necessary to maintain a romantic bond (e.g. caregiving, appropriate attachment), although these skills are not strongly developed until late adolescence.[173] Long-term relationships allow adolescents to gain the skills necessary for high-quality relationships later in life[174] and develop feelings of self-worth. Overall, positive romantic relationships among adolescents can result in long-term benefits. High-quality romantic relationships are associated with higher commitment in early adulthood[175] and are positively associated with self-esteem, self-confidence, and social competence.[176][177] For example, an adolescent with positive self-confidence is likely to consider themselves a more successful partner, whereas negative experiences may lead to low confidence as a romantic partner.[178] Adolescents often date within their demographic in regards to race, ethnicity, popularity, and physical attractiveness.[179] However, there are traits in which certain individuals, particularly adolescent girls, seek diversity. While most adolescents date people approximately their own age, boys typically date partners the same age or younger; girls typically date partners the same age or older.[170]

Some researchers are now focusing on learning about how adolescents view their own relationships and sexuality; they want to move away from a research point of view that focuses on the problems associated with adolescent sexuality.[why?] College Professor Lucia O'Sullivan and her colleagues found that there were no significant gender differences in the relationship events adolescent boys and girls from grades 7-12 reported.[180] Most teens said they had kissed their partners, held hands with them, thought of themselves as being a couple and told people they were in a relationship. This means that private thoughts about the relationship as well as public recognition of the relationship were both important to the adolescents in the sample. Sexual events (such as sexual touching, sexual intercourse) were less common than romantic events (holding hands) and social events (being with one's partner in a group setting). The researchers state that these results are important because the results focus on the more positive aspects of adolescents and their social and romantic interactions rather than focusing on sexual behavior and its consequences.[180]

Adolescence marks a time of sexual maturation, which manifests in social interactions as well. While adolescents may engage in casual sexual encounters (often referred to as hookups), most sexual experience during this period of development takes place within romantic relationships.[181] Adolescents can use technologies and social media to seek out romantic relationships as they feel it is a safe place to try out dating and identity exploration. From these social media encounters, a further relationship may begin.[152] Kissing, hand holding, and hugging signify satisfaction and commitment. Among young adolescents, "heavy" sexual activity, marked by genital stimulation, is often associated with violence, depression, and poor relationship quality.[182][183] This effect does not hold true for sexual activity in late adolescence that takes place within a romantic relationship.[184] Some research suggest that there are genetic causes of early sexual activity that are also risk factors for delinquency, suggesting that there is a group who are at risk for both early sexual activity and emotional distress. For older adolescents, though, sexual activity in the context of romantic relationships was actually correlated with lower levels of deviant behavior after controlling for genetic risks, as opposed to sex outside of a relationship (hook-ups)[185]

Dating violence is fairly prevalent within adolescent relationships. When surveyed, 10-45% of adolescents reported having experienced physical violence in the context of a relationship while a quarter to a third of adolescents reported having experiencing psychological aggression. This reported aggression includes hitting, throwing things, or slaps, although most of this physical aggression does not result in a medical visit. Physical aggression in relationships tends to decline from high school through college and young adulthood. In heterosexual couples, there is no significant difference between the rates of male and female aggressors, unlike in adult relationships.[186][187][188]

In contemporary society, adolescents also face some risks as their sexuality begins to transform. While some of these, such as emotional distress (fear of abuse or exploitation) and sexually transmitted infections/diseases (STIs/STDs), including HIV/AIDS, are not necessarily inherent to adolescence, others such as teenage pregnancy (through non-use or failure of contraceptives) are seen as social problems in most western societies. One in four sexually active teenagers will contract an STI.[189] Adolescents in the United States often chose "anything but intercourse" for sexual activity because they mistakenly believe it reduces the risk of STIs. Across the country, clinicians report rising diagnoses of herpes and human papillomavirus (HPV), which can cause genital warts, and is now thought to affect 15 percent of the teen population. Girls 15 to 19 have higher rates of gonorrhea than any other age group. One-quarter of all new HIV cases occur in those under the age of 21.[189] Multrine also states in her article that according to a March survey by the Kaiser Family Foundation, eighty-one percent of parents want schools to discuss the use of condoms and contraception with their children. They also believe students should be able to be tested for STIs. Furthermore, teachers want to address such topics with their students. But, although 9 in 10 sex education instructors across the country believe that students should be taught about contraceptives in school, over one quarter report receiving explicit instructions from school boards and administrators not to do so. According to anthropologist Margaret Mead, the turmoil found in adolescence in Western society has a cultural rather than a physical cause; they reported that societies where young women engaged in free sexual activity had no such adolescent turmoil.

Culture

Summary

There are certain characteristics of adolescent development that are more rooted in culture than in human biology or cognitive structures. Culture has been defined as the "symbolic and behavioral inheritance received from the past that provides a community framework for what is valued".[190] Culture is learned and socially shared, and it affects all aspects of an individual's life.[191] Social responsibilities, sexual expression, and belief system development, for instance, are all things that are likely to vary by culture. Furthermore, distinguishing characteristics of youth, including dress, music and other uses of media, employment, art, food and beverage choices, recreation, and language, all constitute a youth culture.[191] For these reasons, culture is a prevalent and powerful presence in the lives of adolescents, and therefore we cannot fully understand today's adolescents without studying and understanding their culture.[191] However, "culture" should not be seen as synonymous with nation or ethnicity. Many cultures are present within any given country and racial or socioeconomic group. Furthermore, to avoid ethnocentrism, researchers must be careful not to define the culture's role in adolescence in terms of their own cultural beliefs.[192]

Autonomy

The degree to which adolescents are perceived as autonomous beings varies widely by culture, as do the behaviors that represent this emerging autonomy. Psychologists have identified three main types of autonomy: emotional independence, behavioral autonomy, and cognitive autonomy.[193] Emotional autonomy is defined in terms of an adolescent's relationships with others, and often includes the development of more mature emotional connections with adults and peers.[193] Behavioral autonomy encompasses an adolescent's developing ability to regulate his or her own behavior, to act on personal decisions, and to self-govern. Cultural differences are especially visible in this category because it concerns issues of dating, social time with peers, and time-management decisions.[193] Cognitive autonomy describes the capacity for an adolescent to partake in processes of independent reasoning and decision-making without excessive reliance on social validation.[193] Converging influences from adolescent cognitive development, expanding social relationships, an increasingly adultlike appearance, and the acceptance of more rights and responsibilities enhance feelings of autonomy for adolescents.[193] Proper development of autonomy has been tied to good mental health, high self-esteem, self-motivated tendencies, positive self-concepts, and self-initiating and regulating behaviors.[193] Furthermore, it has been found that adolescents' mental health is best when their feelings about autonomy match closely with those of their parents.[194]

A questionnaire called the teen timetable has been used to measure the age at which individuals believe adolescents should be able to engage in behaviors associated with autonomy.[195] This questionnaire has been used to gauge differences in cultural perceptions of adolescent autonomy, finding, for instance, that White parents and adolescents tend to expect autonomy earlier than those of Asian descent.[195] It is, therefore, clear that cultural differences exist in perceptions of adolescent autonomy, and such differences have implications for the lifestyles and development of adolescents. In sub-Saharan African youth, the notions of individuality and freedom may not be useful in understanding adolescent development. Rather, African notions of childhood and adolescent development are relational and interdependent.[196]

Social roles and responsibilities

Portrait of a noble girl c. 1571

The lifestyle of an adolescent in a given culture is profoundly shaped by the roles and responsibilities he or she is expected to assume. The extent to which an adolescent is expected to share family responsibilities is one large determining factor in normative adolescent behavior. For instance, adolescents in certain cultures are expected to contribute significantly to household chores and responsibilities.[197] Household chores are frequently divided into self-care tasks and family-care tasks. However, specific household responsibilities for adolescents may vary by culture, family type, and adolescent age.[198] Some research has shown that adolescent participation in family work and routines has a positive influence on the development of an adolescent's feelings of self-worth, care, and concern for others.[197]

In addition to the sharing of household chores, certain cultures expect adolescents to share in their family's financial responsibilities. According to family economic and financial education specialists, adolescents develop sound money management skills through the practices of saving and spending money, as well as through planning ahead for future economic goals.[199] Differences between families in the distribution of financial responsibilities or provision of allowance may reflect various social background circumstances and intrafamilial processes, which are further influenced by cultural norms and values, as well as by the business sector and market economy of a given society.[200] For instance, in many developing countries it is common for children to attend fewer years of formal schooling so that, when they reach adolescence, they can begin working.[201]

While adolescence is a time frequently marked by participation in the workforce, the number of adolescents in the workforce is much lower now than in years past as a result of increased accessibility and perceived importance of formal higher education.[202] For example, half of all 16-year-olds in China were employed in 1980, whereas less than one fourth of this same cohort were employed in 1990.[202]

Furthermore, the amount of time adolescents spend on work and leisure activities varies greatly by culture as a result of cultural norms and expectations, as well as various socioeconomic factors. American teenagers spend less time in school or working and more time on leisure activities—which include playing sports, socializing, and caring for their appearance—than do adolescents in many other countries.[203] These differences may be influenced by cultural values of education and the amount of responsibility adolescents are expected to assume in their family or community.

Time management, financial roles, and social responsibilities of adolescents are therefore closely connected with the education sector and processes of career development for adolescents, as well as to cultural norms and social expectations. In many ways, adolescents' experiences with their assumed social roles and responsibilities determine the length and quality of their initial pathway into adult roles.[204]

Belief system development

Adolescence is frequently characterized by a transformation of an adolescent's understanding of the world, the rational direction towards a life course, and the active seeking of new ideas rather than the unquestioning acceptance of adult authority.[205] An adolescent begins to develop a unique belief system through his or her interaction with social, familial, and cultural environments.[206] While organized religion is not necessarily a part of every adolescent's life experience, youth are still held responsible for forming a set of beliefs about themselves, the world around them, and whatever higher powers they may or may not believe in.[205] This process is often accompanied or aided by cultural traditions that intend to provide a meaningful transition to adulthood through a ceremony, ritual, confirmation, or rite of passage.[207]

Sexuality

Many cultures define the transition into adultlike sexuality by specific biological or social milestones in an adolescent's life. For example, menarche (the first menstrual period of a female), or semenarche (the first ejaculation of a male) are frequent sexual defining points for many cultures. In addition to biological factors, an adolescent's sexual socialization is highly dependent upon whether their culture takes a restrictive or permissive attitude toward teen or premarital sexual activity. In the United States specifically, adolescents are said to have "raging hormones" that drive their sexual desires. These sexual desires are then dramatized regarding teen sex and seen as "a site of danger and risk; that such danger and risk is a source of profound worry among adults".[208] There is little to no normalization regarding teenagers having sex in the U.S., which causes conflict in how adolescents are taught about sex education. There is a constant debate about whether abstinence-only sex education or comprehensive sex education should be taught in schools and this stems back to whether or not the country it is being taught in is permissive or restrictive. Restrictive cultures overtly discourage sexual activity in unmarried adolescents or until an adolescent undergoes a formal rite of passage. These cultures may attempt to restrict sexual activity by separating males and females throughout their development, or through public shaming and physical punishment when sexual activity does occur.[166][209] In less restrictive cultures, there is more tolerance for displays of adolescent sexuality, or of the interaction between males and females in public and private spaces. Less restrictive cultures may tolerate some aspects of adolescent sexuality, while objecting to other aspects. For instance, some cultures find teenage sexual activity acceptable but teenage pregnancy highly undesirable. Other cultures do not object to teenage sexual activity or teenage pregnancy, as long as they occur after marriage.[210] In permissive societies, overt sexual behavior among unmarried teens is perceived as acceptable, and is sometimes even encouraged.[210] Regardless of whether a culture is restrictive or permissive, there are likely to be discrepancies in how females versus males are expected to express their sexuality. Cultures vary in how overt this double standard is—in some it is legally inscribed, while in others it is communicated through social convention.[211] Lesbian, gay, bisexual and transgender youth face much discrimination through bullying from those unlike them and may find telling others that they are gay to be a traumatic experience.[212] The range of sexual attitudes that a culture embraces could thus be seen to affect the beliefs, lifestyles, and societal perceptions of its adolescents.

General issues

Adolescence is a period frequently marked by increased rights and privileges for individuals. While cultural variation exists for legal rights and their corresponding ages, considerable consistency is found across cultures. Furthermore, since the advent of the Convention on the Rights of the Child in 1989 (children here defined as under 18), almost every country in the world (except the U.S. and South Sudan) has legally committed to advancing an anti-discriminatory stance towards young people of all ages. This includes protecting children against unchecked child labor, enrollment in the military, prostitution, and pornography. In many societies, those who reach a certain age (often 18, though this varies) are considered to have reached the age of majority and are legally regarded as adults who are responsible for their actions. People below this age are considered minors or children. A person below the age of majority may gain adult rights through legal emancipation.

The legal working age in Western countries is usually 14 to 16, depending on the number of hours and type of employment under consideration. Many countries also specify a minimum school leaving age, at which a person is legally allowed to leave compulsory education. This age varies greatly cross-culturally, spanning from 10 to 18, which further reflects the diverse ways formal education is viewed in cultures around the world.

In most democratic countries, a citizen is eligible to vote at age 18. In a minority of countries, the voting age is as low as 16 (for example, Brazil), and at one time was as high as 25 in Uzbekistan.

The age of consent to sexual activity varies widely between jurisdictions, ranging from 12 to 20 years, as does the age at which people are allowed to marry.[213] Specific legal ages for adolescents that also vary by culture are enlisting in the military, gambling, and the purchase of alcohol, cigarettes or items with parental advisory labels. It should be noted that the legal coming of age often does not correspond with the sudden realization of autonomy; many adolescents who have legally reached adult age are still dependent on their guardians or peers for emotional and financial support. Nonetheless, new legal privileges converge with shifting social expectations to usher in a phase of heightened independence or social responsibility for most legal adolescents.

Alcohol and illicit drug use

Prevalence

Following a steady decline, beginning in the late 1990s up through the mid-2000s, illicit drug use among adolescents has been on the rise in the U.S. Aside from alcohol, marijuana is the most commonly indulged drug habit during adolescent years. Data collected by the National Institute on Drug Abuse shows that between the years of 2007 and 2011, marijuana use grew from 5.7% to 7.2% among 8th grade students; among 10th grade students, from 14.2% to 17.6%; and among 12th graders, from 18.8% to 22.6%.[214] Additional, recent years have seen a surge in popularity of MDMA; between 2010 and 2011, the use of MDMA increased from 1.4% to 2.3% among high school seniors.[214] The heightened usage of ecstasy most likely ties in at least to some degree with the rising popularity of rave culture.

One significant contribution to the increase in teenage substance abuse is an increase in the availability of prescription medication. With an increase in the diagnosis of behavioral and attentional disorders for students, taking pharmaceutical drugs such as Vicodin and Adderall for pleasure has become a prevalent activity among adolescents: 15.2% of high school seniors report having abused prescription drugs within the past year.[214]

Teenage alcohol drug use is currently at an all-time low. Out of a polled body of students, 4.4% of 8th graders reported having been on at least one occasion been drunk within the previous month; for 10th graders, the number was 13.7%, and for 12th graders, 25%.[214] More drastically, cigarette smoking has become a far less prevalent activity among American middle- and high-school students; in fact, a greater number of teens now smoke marijuana than smoke cigarettes, with one recent study showing a respective 15.2% versus 11.7% of surveyed students.[214] Recent studies have shown that male late adolescents are far more likely to smoke cigarettes rather than females. The study indicated that there was a discernible gender difference in the prevalence of smoking among the students. The finding of the study show that more males than females began smoking when they were in primary and high schools whereas most females started smoking after high school.[215] This may be attributed to recent changing social and political views towards marijuana; issues such as medicinal use and legalization have tended towards painting the drug in a more positive light than historically, while cigarettes continue to be vilified due to associated health risks.

Different drug habits often relate to one another in a highly significant manner. It has been demonstrated that adolescents who drink at least to some degree may be as much as sixteen times more likely than non-drinkers to experiment with illicit drugs.[216]

Social influence

Irish teenagers over 18 hanging around outside a bar. People under 18 are not allowed to drink outside the home; this is not strictly enforced in Ireland.

Peer acceptance and social norms gain a significantly greater hand in directing behavior at the onset of adolescence; as such, the alcohol and illegal drug habits of teens tend to be shaped largely by the substance use of friends and other classmates. In fact, studies suggest that more significantly than actual drug norms, an individual's perception of the illicit drug use by friends and peers is highly associated with his or her own habits in substance use during both middle and high school, a relationship that increases in strength over time.[217] Whereas social influences on alcohol use and marijuana use tend to work directly in the short term, peer and friend norms on smoking cigarettes in middle school have a profound effect on one's own likelihood to smoke cigarettes well into high school.[217] Perhaps the strong correlation between peer influence in middle school and cigarette smoking in high school may be explained by the addictive nature of cigarettes, which could lead many students to continue their smoking habits from middle school into late adolescence.

Demographic factors

Until mid-to-late adolescence, boys and girls show relatively little difference in drinking motives.[218] Distinctions between the reasons for alcohol consumption of males and females begin to emerge around ages 14–15; overall, boys tend to view drinking in a more social light than girls, who report on average a more frequent use of alcohol as a coping mechanism.[218] The latter effect appears to shift in late adolescence and onset of early adulthood (20–21 years of age); however, despite this trend, age tends to bring a greater desire to drink for pleasure rather than coping in both boys and girls.[218]

Drinking habits and the motives behind them often reflect certain aspects of an individual's personality; in fact, four dimensions of the Five-Factor Model of personality demonstrate associations with drinking motives (all but 'Openness'). Greater enhancement motives for alcohol consumption tend to reflect high levels of extraversion and sensation-seeking in individuals; such enjoyment motivation often also indicates low conscientiousness, manifesting in lowered inhibition and a greater tendency towards aggression. On the other hand, drinking to cope with negative emotional states correlates strongly with high neuroticism and low agreeableness.[218] Alcohol use as a negative emotion control mechanism often links with many other behavioral and emotional impairments, such as anxiety, depression, and low self-esteem.[218]

Research has generally shown striking uniformity across different cultures in the motives behind teen alcohol use. Social engagement and personal enjoyment appear to play a fairly universal role in adolescents' decision to drink throughout separate cultural contexts. Surveys conducted in Argentina, Hong Kong, and Canada have each indicated the most common reason for drinking among adolescents to relate to pleasure and recreation; 80% of Argentinian teens reported drinking for enjoyment, while only 7% drank to improve a bad mood.[218] The most prevalent answers among Canadian adolescents were to "get in a party mood," 18%; "because I enjoy it," 16%; and "to get drunk," 10%.[218] In Hong Kong, female participants most frequently reported drinking for social enjoyment, while males most frequently reported drinking to feel the effects of alcohol.[218]

Media

Body image

Teenage girl texting

Much research has been conducted on the psychological ramifications of body image on adolescents. Modern day teenagers are exposed to more media on a daily basis than any generation before them. Recent studies have indicated that the average teenager watches roughly 1500 hours of television per year.[219] As such, modern day adolescents are exposed to many representations of ideal, societal beauty. The concept of a person being unhappy with their own image or appearance has been defined as "body dissatisfaction". In teenagers, body dissatisfaction is often associated with body mass, low self-esteem, and atypical eating patterns.[220] Scholars continue to debate the effects of media on body dissatisfaction in teens.[221][222]

Media profusion

Because exposure to media has increased over the past decade, adolescents' utilization of computers, cell phones, stereos and televisions to gain access to various mediums of popular culture has also increased. Almost all American households have at least one television, more than three-quarters of all adolescents' homes have access to the Internet, and more than 90% of American adolescents use the Internet at least occasionally.[223] As a result of the amount of time adolescents spend using these devices, their total media exposure is high. In the last decade, the amount of time that adolescents spend on the computer has greatly increased.[224] Online activities with the highest rates of use among adolescents are video games (78% of adolescents), email (73%), instant messaging (68%), social networking sites (65%), news sources (63%), music (59%), and videos (57%).

Social networking

In the 2000s, social networking sites proliferated and a high proportion of adolescents used them: as of 2012 73% of 12–17 year olds reported having at least one social networking profile;[225] two-thirds (68%) of teens texted every day, half (51%) visited social networking sites daily, and 11% sent or received tweets at least once every day. More than a third (34%) of teens visited their main social networking site several times a day. One in four (23%) teens were "heavy" social media users, meaning they used at least two different types of social media each and every day.[226]

Although research has been inconclusive, some findings have indicated that electronic communication negatively affects adolescents' social development, replaces face-to-face communication, impairs their social skills, and can sometimes lead to unsafe interaction with strangers. A 2015 review reported that "adolescents lack awareness of strategies to cope with cyberbullying, which has been consistently associated with an increased likelihood of depression."[227] Studies have shown differences in the ways the internet negatively impacts the adolescents' social functioning. Online socializing tends to make girls particularly vulnerable, while socializing in Internet cafés seems only to affect boys academic achievement. However, other research suggests that Internet communication brings friends closer and is beneficial for socially anxious teens, who find it easier to interact socially online.[228] The more conclusive finding has been that Internet use has a negative effect on the physical health of adolescents, as time spent using the Internet replaces time doing physical activities. However, the Internet can be significantly useful in educating teens because of the access they have to information on many various topics.

Transitions into adulthood

A broad way of defining adolescence is the transition from child-to-adulthood. According to Hogan & Astone (1986), this transition can include markers such as leaving school, starting a full-time job, leaving the home of origin, getting married, and becoming a parent for the first time.[229] However, the time frame of this transition varies drastically by culture. In some countries, such as the United States, adolescence can last nearly a decade, but in others, the transition—often in the form of a ceremony—can last for only a few days.[230]

Some examples of social and religious transition ceremonies that can be found in the U.S., as well as in other cultures around the world, are Confirmation, Bar and Bat Mitzvahs, Quinceañeras, sweet sixteens, cotillions, and débutante balls. In other countries, initiation ceremonies play an important role, marking the transition into adulthood or the entrance into adolescence. This transition may be accompanied by obvious physical changes, which can vary from a change in clothing to tattoos and scarification.[210] Furthermore, transitions into adulthood may also vary by gender, and specific rituals may be more common for males or for females. This illuminates the extent to which adolescence is, at least in part, a social construction; it takes shape differently depending on the cultural context, and may be enforced more by cultural practices or transitions than by universal chemical or biological physical changes.

Promoting positive changes in adolescents

At the decision-making point of their lives, youth is susceptible to drug addiction, sexual abuse, peer pressure, violent crimes and other illegal activities. Developmental Intervention Science (DIS) is a fusion of the literature of both developmental and intervention sciences. This association conducts youth interventions that mutually assist both the needs of the community as well as psychologically stranded youth by focusing on risky and inappropriate behaviors while promoting positive self-development along with self-esteem among adolescents.[231]

Criticism

The concept of adolescence has been criticized by experts, such as Robert Epstein, who state that an undeveloped brain is not the main cause of teenagers' turmoils.[232][233] Some have criticized the concept of adolescence because it is a relatively recent phenomenon in human history created by modern society,[234][235][236][237] and have been highly critical of what they view as the infantilization of young adults in American society.[238] In an article for Scientific American, Robert Epstein and Jennifer Ong state that "American-style teen turmoil is absent in more than 100 cultures around the world, suggesting that such mayhem is not biologically inevitable. Second, the brain itself changes in response to experiences, raising the question of whether adolescent brain characteristics are the cause of teen tumult or rather the result of lifestyle and experiences."[239] David Hoshman has also stated in regards to adolescence that brain research "is crucial for a full picture, but it does not provide an ultimate explanation."[240]

Other critics of the concept of adolescence do point at individual differences in brain growth rate, citing that some (though not all) early teens still have infantile undeveloped corpus callosums, concluding that "the adult in *every* adolescent" is too generalizing. These people tend to support the notion that a more interconnected brain makes more precise distinctions (citing Pavlov's comparisons of conditioned reflexes in different species) and that there is a non-arbitrary threshold at which distinctions become sufficiently precise to correct assumptions afterward as opposed to being ultimately dependent on exterior assumptions for communication. They argue that this threshold is the one at which an individual is objectively capable of speaking for himself or herself, as opposed to culturally arbitrary measures of "maturity" which often treat this ability as a sign of "immaturity" merely because it leads to questioning of authorities. These people also stress the low probability of the threshold being reached at a birthday, and instead advocate non-chronological emancipation at the threshold of afterward correction of assumptions.[241] They sometimes cite similarities between "adolescent" behavior and KZ syndrome (inmate behavior in adults in prison camps) such as aggression being explainable by oppression and "immature" financial or other risk behavior being explainable by a way out of captivity being more worth to captive people than any incremental improvement in captivity, and argue that this theory successfully predicted remaining "immature" behavior after reaching the age of majority by means of longer-term traumatization. In this context, they refer to the fallibility of official assumptions about what is good or bad for an individual, concluding that paternalistic "rights" may harm the individual. They also argue that since it never took many years to move from one group to another to avoid inbreeding in the paleolithic, evolutionary psychology is unable to account for a long period of "immature" risk behavior.[242]

^Larson, R., & Wilson, S. (2004). Adolescence across place and time: Globalization and the changing pathways to adulthood. In R. Lerner and L. Steinberg Handbook of adolescent psychology. New York: Wiley

^Shoval, G., Bar-Shira O., Zalsman G., John J. Mann and Chechik G. (2014) Transitions in the transcriptome of the serotonergic and dopaminergic systems in the human brain during adolescence. European Neuropsychopharmacology. (2014). "Transitions in the transcriptome of the serotonergic and dopaminergic systems in the human brain during adolescence". European Neuropsychopharmacology. 24 (7): 1123–32. doi:10.1016/j.euroneuro.2014.02.009. PMID24721318.CS1 maint: Uses authors parameter (link)

^Brown, A. (1975). The development of memory: Knowing, knowing about knowing, and knowing how to know. In H. Reese (Ed.), Advances in child development and behavior (Vol. 10). New York: Academic Press.

^Montemayor, R., Brown, B., & Adams, G. (1985). Changes in identity status and psychological adjustment after leaving home and entering college. Paper presented at the biennial meetings of the Society for Research in Child Development, Toronto.

^Brown, B., & Mounts, N. (1989, April). "Peer groups structures in single versus multiethnic high schools". Paper presented at the biennial meetings of the Society for Research on Adolescence, San Diego.

^Seiffge-Krenke I., Lang J. (2002). Forming and maintaining romantic relations from early adolescence to young adulthood: evidence of a developmental sequence. Presented at Biennial Meeting of the Society for Research on Adolescence, 19th, New Orleans, LA.

^Harden K.; Mendle J. (2011). "Adolescent sexual activity and the development of delinquent behavior: The role of relationship context". Journal of Youth and Adolescence. 40 (7): 825–838. doi:10.1007/s10964-010-9601-y.

^Fasick, Frank A. (February 1994). "On the "Invention" of Adolescence". Journal of Early Adolescence. 14 (1): 6–23. doi:10.1177/0272431694014001002. "[...] the application of technology to increase productivity, the affluence generated by it, and the related structural changes in society have contributed to the creation of adolescence in the North American urban-industrial society."

^Demos, John; Demos, Virginia (1969). "Adolescence in Historical Perspective". Journal of Marriage and Family. 31 (4): 632–638. doi:10.2307/349302. "The idea of adolescence is today one of our most widely held and deeply imbedded assumptions about the process of human development. Indeed most of us treat it not as an idea but as a fact. [...] The concept of adolescence, as generally understood and applied, did not exist before the last two decades of the nineteenth century."

1.
My Chemical Romance
–
My Chemical Romance was an American rock band from New Jersey, active from 2001 to 2013. The bands best-known lineup consisted of lead vocalist Gerard Way, guitarists Ray Toro and Frank Iero, bassist Mikey Way and drummer Bob Bryar. Founded by Gerard, Mikey, Toro, Matt Pelissier, and later joined by Iero and they signed with Reprise Records the next year and released their major label debut Three Cheers for Sweet Revenge in 2004. Shortly after the release, Pelissier was replaced by Bob Bryar. A commercial success, the album was awarded platinum status over a year later, after the bands split, a greatest hits album entitled May Death Never Stop You was released in March 2014. A tenth anniversary reissue of The Black Parade was released in September 2016 titled The Black Parade/Living with Ghosts, the band was formed by frontman Gerard Way and drummer Matt Pelissier soon after the September 11 attacks. Witnessing the World Trade Center towers fall influenced Ways life to the extent that he decided to start a band, the first recording sessions were undertaken in Pelissiers attic, where the songs Our Lady of Sorrows and Cubicles were recorded. The band refers to those sessions as The Attic Demos, after hearing the demo and dropping out of college, Mikey Way decided to join the band. While with Eyeball Records, the band met Frank Iero, the lead vocalist and guitarist for Pencey Prep, following Pencey Preps split in 2002, Iero became a member of My Chemical Romance, just days prior to the recording of the bands debut album. They recorded their album, I Brought You My Bullets, You Brought Me Your Love. The album was produced by Thursday frontman Geoff Rickley after the band became friends with him while playing shows in New Jersey, Iero played guitar on two of the tracks, one of which was Early Sunsets Over Monroeville. During this time, the band was booked at the venue, Big Daddys. My Chemical Romance offered free downloads through PureVolume and the social networking website MySpace, in 2003, the band signed a deal with Reprise Records. Following a tour with Avenged Sevenfold, the band working on their second album. Released in 2004, the album went platinum in just over a year, the band released four singles from the album, Im Not Okay, Thank You for the Venom, Helena, and The Ghost of You. After returning from a tour of Japan in July 2004, the band replaced Matt Pelissier with Bob Bryar. At the beginning of 2005, the band was featured on the first Taste of Chaos tour and they then co-headlined Warped Tour 2005 with Fall Out Boy and co-headlined a tour with Alkaline Trio and Reggie and the Full Effect around the US. In March 2006, the album Life on the Murder Scene was released, incorporating a CD and it included one documentary DVD chronicling the bands history, and a second DVD with music videos, the making of their videos and live performances

2.
Teenagers (song)
–
Teenagers is the fourth and final single and the eleventh track from My Chemical Romances third studio album, The Black Parade. It is the third United States single from the album, but it is the single released in the United Kingdom. This song is the eleventh overall single. The song was released to radio on May 15,2007, despite charting at #67 on the US Billboard Hot 100, Teenagers is their highest single on the Pop 100 at #23. Gerard Way is quoted as saying that he wrote the song after finding himself in a New York subway car full of high schoolers, That was the first time I felt old. I was nervous and I was a target. I felt like I had become a parent figure or part of the problem, about the relationship between the song and concerns about gun violence, Way said, This song was #25 on Rolling Stones list of the 100 Best Songs of 2007. This song was also #80 on MTV Asias list of Top 100 Hits of 2007, the single is certified double Platinum by the RIAA. My Chemical Romance surprised many critics by the style of Teenagers. It incorporates elements of pop punk, hard rock and 8 bar blues and this earned them mostly positive reviews from critics. A reviewer from NME wrote, Some bands go out of their way to do a song with a sound theyre never bound to do and my Chemical Romance tried a substantially different sound for this song, and it paid off. The message is simple, the chorus is catchy and Ray Toros solo joins the chorus, the song managed to grab 5 stars in both NME and AbsolutePunk. net as well as 4/5 from IMDb. The song entered the Bubbling Under Hot 100 Singles chart at #2, before debuting at #87 on the Hot 100 the following week as the Hot Shot debut of the week and it has reached #23 on the Pop 100, and #13 on Modern Rock Tracks. It also debuted at #42 in the UK, and became the fourth straight top 20 hit from The Black Parade and their third top ten hit from the album. It debuted at number 16 on the ARIA Singles Chart, the music video opens with an almost shot-for-shot tribute to the first scene of Pink Floyds film The Wall. Further links to The Wall are seen when cheerleaders don gas masks similar to those worn by the teenaged, the video was posted by the band via their YouTube channel on May 30,2007 and has since obtained over 100 million views. Sometime around November 1,2007, the video passed the Famous Last Words video as the third most played video on the site and this version of the video cut out the word shit. The MTV version differs from the YouTube version, notably the teenagers breaking in was cut out, as well as the gun, shit. The video has debuted on Total Request Live and this video made its world premiere in New Zealand, which was also the first country in which The Black Parade reached number one

3.
Teenage (film)
–
Teenage is a 2013 documentary film directed by Matt Wolf and based on Jon Savages book Teenage, The Creation of Youth Culture. In the documentary, Wolf attempts to bring to life the prehistory of youth culture which preceded and evolved into the concept of culture in the 1950s. The film had its premiere at the Tribeca Film Festival on April 20,2013. and was released in a limited release and through video on demand on March 14,2014. The film documents the evolution of culture from the early twentieth century starting in 1904 until the end of WWII in 1945 when the concept of the teenager was developed. Youth culture and movements through four decades of evolution are examined as they emerged primarily in European countries, the film documents the history of German youth movements like the Wandervogel, the Hitler Youth, and the Swing Kids of Hamburg. It also examines the role young people played in the resistance against the Nazis, showcasing Sophie Scholl and her organisation White Rose, as part of its retrospective into the early UK youth culture, the film looks into the lives of Brenda Dean Paul and the bright young things. American youth movements such as the flappers, victory girls and Boy Scouts are also included in the film. In the making of his film, Wolf used those parts from Savages book that were found in archival film of the era so that they could be shown in their original form on the screen. Wolfs documentary does not follow a historical account of the events but develops its story by meandering through the musings. For narration, the film uses first-person accounts derived from personal diaries, films, in the case of Brend Dean Paul, Wolf uses her autobiography, published in 1935, to narrate her segment in the film. In a similar vein, the Hamburg Swing Kids are shown in the documentary through their self-made movies, there is no single narrator for the film. Instead four actors use their voices to different people. It was pitched at the 2011 MeetMarket as part of Sheffield Doc/Fest, Wolf has described his film as a living collage. He replied that he considers Brenda Dean Paul as a proto-Lindsay Lohan and he also said that he considers Melita Maschmann, a Hitler Youth leader, as a very extreme character who rebelled against her parents by joining Hitlers Youth. In the same interview, Wolf also said that he was intrigued by Warren Hall because he was an ordinary kid, unlike the other characters who were larger than life. According to Wolf, Warren, as a boy scout, just wanted to fit in, in another interview with the New York Times Style Magazine, when asked what the youth movements such as the Boy Scouts the Wandervogel, the Jitterbugs etc. The Washington Post review remarks that t’s hard to believe that not so long ago, the reviewer ends the critique by commenting that the pictures of teens of years past have the same expressions as those of modern youth, which reflect similar beliefs. The Guardian remarks that in the documentary, Wolf concentrates on the strange, bubbling energy and intensity, in August 2013, Oscilloscope Laboratories had acquired distribution rights to the film

4.
Oslo
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Oslo is the capital and the most populous city in Norway. It constitutes both a county and a municipality, founded in the year 1040, and established as a kaupstad or trading place in 1048 by Harald Hardrada, the city was elevated to a bishopric in 1070 and a capital under Haakon V of Norway around 1300. Personal unions with Denmark from 1397 to 1523 and again from 1536 to 1814, after being destroyed by a fire in 1624, the city was moved closer to Akershus Fortress during the reign of Christian IV of Denmark and renamed Christiania in his honour. It was established as a municipality on 1 January 1838, following a spelling reform, it was known as Kristiania from 1877 to 1925, at which time its original Norwegian name was restored. Oslo is the economic and governmental centre of Norway, the city is also a hub of Norwegian trade, banking, industry and shipping. It is an important centre for industries and maritime trade in Europe. The city is home to companies within the maritime sector, some of which are among the worlds largest shipping companies, shipbrokers. Oslo is a city of the Council of Europe and the European Commission intercultural cities programme. Oslo is considered a city and ranked Beta World City in studies carried out by the Globalization and World Cities Study Group. It was ranked one in terms of quality of life among European large cities in the European Cities of the Future 2012 report by fDi magazine. A survey conducted by ECA International in 2011 placed Oslo as the second most expensive city in the world for living expenses after Tokyo. In 2013 Oslo tied with the Australian city of Melbourne as the fourth most expensive city in the world, as of January 1,2016, the municipality of Oslo has a population of 658,390, while the population of the citys urban area was 942,084. The metropolitan area had an population of 1.71 million. The population was during the early 2000 increasing at record rates and this growth stems for the most part from international immigration and related high birth rates, but also from intra-national migration. The immigrant population in the city is growing faster than the Norwegian population. As of January 1,2016, the municipality of Oslo has a population of 658,390, the urban area extends beyond the boundaries of the municipality into the surrounding county of Akershus, the total population of this agglomeration is 942,084. To the north and east, wide forested hills rise above the city giving the location the shape of a giant amphitheatre. The urban municipality of Oslo and county of Oslo are two parts of the entity, making Oslo the only city in Norway where two administrative levels are integrated

5.
Human development (biology)
–
Human development is the process of growing to maturity. In biological terms, this entails growth from a zygote to an adult human being. Fertilization occurs when the sperm enters the ovums membrane. The genetical material of the sperm and egg that combine to form a cell, called a zygote. The germinal stage refers to the time from fertilization, through the development of the early embryo, the germinal stage is over at about 10 days of gestation. The zygote contains a full complement of genetic material and develops into the embryo, briefly, embryonic developments have four stages, the morula stage, the bastula stage, the gastrula stage, and the neurula stage. Prior to implantation, the remains in a protein shell, the zona pellucida. A week after fertilization the embryo still has not grown in size and this induces a decidual reaction, wherein the uterine cells proliferate and surround the embryo thus causing it to become embedded within the uterine tissue. The embryo, meanwhile, proliferates and develops both into embryonic and extra-embryonic tissue, the forming the fetal membranes and the placenta. In humans, the embryo is referred to as a fetus in the stages of prenatal development. The transition from embryo to fetus is arbitrarily defined as occurring 8 weeks after fertilization, in comparison to the embryo, the fetus has more recognizable external features and a set of progressively developing internal organs. A nearly identical process occurs in other species, auxology Child development Developmental biology Embryogenesis Life-history theory

6.
Human embryogenesis
–
Human embryogenesis is the process of cell division and cellular differentiation of the embryo that occurs during the early stages of development. In biological terms, human development entails growth from a zygote to an adult human being. Fertilisation occurs when the cell successfully enters and fuses with an egg cell. The genetic material of the sperm and egg then combine to form a single cell called a zygote, embryogenesis covers the first eight weeks of development, at the beginning of the ninth week the embryo is termed a fetus. Human embryology is the study of development during the first eight weeks after fertilisation. The normal period of gestation is nine months or 38 weeks, the germinal stage refers to the time from fertilization through the development of the early embryo until implantation is completed in the uterus. The germinal stage takes around 10 days, during this stage, the zygote begins to divide, in a process called cleavage. A blastocyst is then formed and implanted in the uterus, embryogenesis continues with the next stage of gastrulation, when the three germ layers of the embryo form in a process called histogenesis, and the processes of neurulation and organogenesis follow. In comparison to the embryo, the fetus has more recognizable external features, the entire process of embryogenesis involves coordinated spatial and temporal changes in gene expression, cell growth and cellular differentiation. A nearly identical process occurs in species, especially among chordates. Fertilization takes place when the spermatozoon has entered the ovum. This usually takes place in the ampulla of one of the fallopian tubes, the 46 chromosomes undergo changes prior to the mitotic division which leads to the formation of the embryo having two cells. Successful fertilization is enabled by three processes, which act as controls to ensure species-specificity. The first is that of chemotaxis which directs the movement of the sperm towards the ovum, secondly there is an adhesive compatibility between the sperm and the egg. The entry of the sperm causes calcium to be released which blocks entry to other sperm cells, a parallel reaction takes place in the ovum called the zona reaction. This sees the release of granules that release enzymes which digest sperm receptor proteins. The granules also fuse with the membrane and modify the zona pellucida in such a way as to prevent further sperm entry. The beginning of the process is marked when the zygote divides through mitosis into two cells

7.
Fetus
–
A fetus is a stage in the prenatal development of viviparous organisms. In human development, a fetus or foetus is a human between the embryonic state and birth. The fetal stage of development tends to be taken as beginning at the age of eleven weeks. In biological terms, however, prenatal development is a continuum, the use of the term fetus generally implies that an embryo has developed to the point of being recognizable as a human, this is the point usually taken to be the ninth week after fertilization. A fetus is also characterized by the presence of all the body organs, though they will not yet be fully developed and functional. The word fetus is from the Latin fētus, the British, Irish, and Commonwealth spelling is foetus, which has been in use since at least 1594. It arose as a hypercorrection based on an incorrect etymology that may have originated with an error by Isidore of Seville in AD620 and this spelling is the most common in most Commonwealth nations, except in the medical literature, where fetus is used. The etymologically accurate original spelling fetus is used in Canada and the United States, in addition, fetus is now the standard English spelling throughout the world in medical journals. The spelling faetus was used historically, in humans, the fetal stage commences at the beginning of the ninth week. At the start of the stage, the fetus is typically about 30 millimetres in length from crown to rump. The head makes up half of the fetus size. Breathing-like movement of the fetus is necessary for stimulation of lung development, the heart, hands, feet, brain and other organs are present, but are only at the beginning of development and have minimal operation. The genitalia of the starts to form and placenta becomes fully functional during week 9. At this point in development, uncontrolled movements and twitches occur as muscles, the brain, and pathways begin to develop. A woman pregnant for the first time, typically feels fetal movements at about 21 weeks, whereas a woman who has given birth at least once, by the end of the fifth month, the fetus is about 20 cm long. The amount of body fat rapidly increases, thalamic brain connections, which mediate sensory input, form. Bones are fully developed, but are soft and pliable. Iron, calcium, and phosphorus become more abundant, fingernails reach the end of the fingertips

8.
Infant
–
An infant is the more formal or specialised synonym for baby, the very young offspring of a human or other animal. A newborn is, in use, an infant who is only hours, days. In medical contexts, newborn or neonate refers to an infant in the first 28 days after birth, the term applies to premature, full term, and postmature infants, before birth, the term fetus is used. The term infant is typically applied to children under one year of age, however, definitions may vary. When a human child learns to walk, the toddler may be used instead. In British English, infant is a term that can be applied to children aged between four and seven. As a legal term, infancy continues from birth until age 18, a newborns shoulders and hips are wide, the abdomen protrudes slightly, and the arms and legs are relatively long with respect to the rest of their body. In first world nations, the total body length of newborns are 35. 6–50.8 cm. The Apgar score is a measure of a transition from the uterus during the first minutes after birth. In developed countries, the birth weight of a full-term newborn is approximately 3.4 kg. After the first week, healthy term neonates should gain 10–20 grams/day, a newborns head is very large in proportion to the body, and the cranium is enormous relative to his or her face. While the adult human skull is one seventh of the total body length. Normal head circumference for an infant is 33–36 cm at birth. At birth, many regions of the skull have not yet been converted to bone. The two largest are the anterior fontanel, located at the top front portion of the head, and the smaller triangular-shaped posterior fontanel. Later in the life, these bones will fuse together in a natural process. A protein called noggin is responsible for the delay in an infants skull fusion, during labour and birth, the infants skull changes shape to fit through the birth canal, sometimes causing the child to be born with a misshapen or elongated head. It will usually return to normal on its own within a few days or weeks, special exercises sometimes advised by physicians may assist the process

9.
Toddler
–
A toddler is a child 12 to 36 months old. The toddler years are a time of great cognitive, emotional and social development, the word is derived from to toddle, which means to walk unsteadily, like a child of this age. Toddler development can be broken down into a number of interrelated areas, there is reasonable consensus about what these include, Physical, growth or an increase in size. Gross motor, the control of muscles which enable walking, running, jumping and climbing. Fine motor, the ability to control small muscles, enabling the toddler to feed themselves, draw, vision, the ability to see near and far and interpret what is seen. Hearing and speech, the ability to hear and receive information and listen, social, the ability to interact with the world through playing with others, taking turns and fantasy play. Although it is useful to chart defined periods of development, it is necessary to recognize that development exists on a continuum. There is a range of what may be considered normal development. Talking is the milestone of which parents are typically aware. A toddlers first word most often occurs around 12 months, the child will then continue to steadily add to his or her vocabulary until around the age of 18 months when language increases rapidly. He or she may learn as many as 7–9 new words a day, around this time, toddlers generally know about 50 words. At 21 months is when toddlers begin to incorporate two word phrases into their vocabulary, such as I go, mama give, and baby play, before going to sleep they often engage in a monologue called crib talk in which they practice conversational skills. At this age, children are becoming very proficient at conveying their wants, there are several other important milestones that are achieved in this time period that parents tend not to emphasize as much as walking and talking. Gaining the ability to point at whatever it is the child wants you to see shows huge psychological gains in a toddler and this generally happens before a childs first birthday. This age is sometimes referred to as the twos, because of the temper tantrums for which they are famous. This stage can begin as early as nine months old depending on the child, toddlers tend to have temper tantrums because they have such strong emotions but do not know how to express themselves the way that older children and adults do. They also throw tantrums to let know that they are free. The toddler is discovering that they are a separate being from their parent and are testing their boundaries in learning the way the world around them works and this time between the ages of two and five when they are reaching for independence repeats itself during adolescence

10.
Preadolescence
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Preadolescence, also known as pre-teen or tween, is a stage of human development following early childhood and preceding adolescence. It commonly ends with the beginning of puberty, but may also be defined as ending with the start of the teenage years, for example, dictionary definitions generally designate it as 10–13 years. Preadolescence can bring its own challenges and anxieties, being prepubescent is not the same thing as being preadolescent. Instead, prepubescent is a term for boys and girls who have not developed secondary sex characteristics, preadolescence may also be defined as the period from 9 to 14 years. The point at which a child becomes an adolescent is defined by the onset of puberty or by the beginning of the teenage stage, adolescence is also viewed as ending with the teenage stage. However, in individuals, puberty begins in the preadolescence years. Studies indicate that the onset of puberty has been one year earlier with each generation since the 1950s, one can also distinguish middle childhood and preadolescence – middle childhood from approximately 5–8 years, as opposed to the time children are generally considered to reach preadolescence. While known as preadolescent in psychology, the terms preteen, preteenager or tween are common in everyday use, a preteen or preteenager is a person 12 and under. Generally, the term is restricted to close to reaching age 12. Tween is an American neologism and marketing term for preteen, which is a blend of between and teen, people within this age range are variously described as tweens, preadolescents, tweenies, preteens, pubescents, junior highers or tweenagers. In this context, the word is either a shortened version of between or a portmanteau of teen and twenty, and in either case has no connection to teens, preteens or the American marketing niche. Preadolescent children in fact have a different view of the world from younger children in many significant ways, typically, theirs is a more realistic view of life than the intense, fantasy-oriented world of earliest childhood. Preadolescents have more mature, sensible, realistic thoughts and actions and they will often have developed a sense of intentionality. The wish and capacity to have an impact, and to act upon that with persistence and this can include more realistic job expectations. Preadolescents may well view human relationships differently, alongside that, they may begin to develop a sense of self-identity, and to have increased feelings of independence, may feel an individual, no longer just one of the family. A different view on morality can emerge, and the child will also show more cooperativeness. The ability to balance ones own needs with those of others in group activities, preadolescents may still suffer tantrums at the age of 13, sometimes leading to rash decisions regarding risky actions. Such decisions may in rare cases result in situations such as accidental death

11.
Adult
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Biologically, an adult is a human or other organism that has reached sexual maturity. In human context, the term adult additionally has meanings associated with social and legal concepts, in contrast to a minor, a legal adult is a person who has attained the age of majority and is therefore regarded as independent, self-sufficient, and responsible. Human adulthood encompasses psychological adult development, conversely, one may legally be an adult but possess none of the maturity and responsibility that may define an adult character. In different cultures there are events that relate passing from being a child to becoming an adult or coming of age. This often encompasses the passing a series of tests to demonstrate that a person is prepared for adulthood, or reaching a specified age, most modern societies determine legal adulthood based on reaching a legally specified age without requiring a demonstration of physical maturity or preparation for adulthood. Historically and cross-culturally, adulthood has been determined primarily by the start of puberty, in the past, a person usually moved from the status of child directly to the status of adult, often with this shift being marked by some type of coming-of-age test or ceremony. After the social construct of adolescence was created, adulthood split into two forms, biological adulthood and social adulthood, thus, there are now two primary forms of adults, biological adults and social adults. Depending on the context, adult can indicate either definition, thus, the base definition of the word adult is the period beginning at puberty. Puberty generally begins around 10 or 11 years of age for girls and 11 or 12 years of age for boys, legally, adulthood means that one can engage in a contract. One can distinguish the legality of acts of a person, or of enabling a young person to carry out that act, by selling, renting out, showing, permitting entrance, allowing participation. There may be distinction between commercially and socially enabling, sometimes there is the requirement of supervision by a legal guardian, or just by an adult. Sometimes there is no requirement, but rather a recommendation, with regard to films with violence, etc. Some cultures in Africa define adulthood at age 13, according to Jewish tradition, adulthood is reached at age 13 for Jewish boys and girls, they are expected to demonstrate preparation for adulthood by learning the Torah and other Jewish practices. The Christian Bible and Jewish scripture contain no age requirement for adulthood or marrying, which includes engaging in sexual activity. The 1983 Code of Canon Law states, A man before he has completed his year of age

12.
Middle age
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In the history of Europe, the Middle Ages or Medieval Period lasted from the 5th to the 15th century. It began with the fall of the Western Roman Empire and merged into the Renaissance, the Middle Ages is the middle period of the three traditional divisions of Western history, classical antiquity, the medieval period, and the modern period. The medieval period is subdivided into the Early, High. Population decline, counterurbanisation, invasion, and movement of peoples, the large-scale movements of the Migration Period, including various Germanic peoples, formed new kingdoms in what remained of the Western Roman Empire. In the seventh century, North Africa and the Middle East—once part of the Byzantine Empire—came under the rule of the Umayyad Caliphate, although there were substantial changes in society and political structures, the break with classical antiquity was not complete. The still-sizeable Byzantine Empire survived in the east and remained a major power, the empires law code, the Corpus Juris Civilis or Code of Justinian, was rediscovered in Northern Italy in 1070 and became widely admired later in the Middle Ages. In the West, most kingdoms incorporated the few extant Roman institutions, monasteries were founded as campaigns to Christianise pagan Europe continued. The Franks, under the Carolingian dynasty, briefly established the Carolingian Empire during the later 8th, the Crusades, first preached in 1095, were military attempts by Western European Christians to regain control of the Holy Land from Muslims. Kings became the heads of centralised nation states, reducing crime and violence, intellectual life was marked by scholasticism, a philosophy that emphasised joining faith to reason, and by the founding of universities. Controversy, heresy, and the Western Schism within the Catholic Church paralleled the conflict, civil strife. Cultural and technological developments transformed European society, concluding the Late Middle Ages, the Middle Ages is one of the three major periods in the most enduring scheme for analysing European history, classical civilisation, or Antiquity, the Middle Ages, and the Modern Period. Medieval writers divided history into periods such as the Six Ages or the Four Empires, when referring to their own times, they spoke of them as being modern. In the 1330s, the humanist and poet Petrarch referred to pre-Christian times as antiqua, leonardo Bruni was the first historian to use tripartite periodisation in his History of the Florentine People. Bruni and later argued that Italy had recovered since Petrarchs time. The Middle Ages first appears in Latin in 1469 as media tempestas or middle season, in early usage, there were many variants, including medium aevum, or middle age, first recorded in 1604, and media saecula, or middle ages, first recorded in 1625. The alternative term medieval derives from medium aevum, tripartite periodisation became standard after the German 17th-century historian Christoph Cellarius divided history into three periods, Ancient, Medieval, and Modern. The most commonly given starting point for the Middle Ages is 476, for Europe as a whole,1500 is often considered to be the end of the Middle Ages, but there is no universally agreed upon end date. English historians often use the Battle of Bosworth Field in 1485 to mark the end of the period

13.
Old age
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Old age refers to ages nearing or surpassing the life expectancy of human beings, and is thus the end of the human life cycle. Terms and euphemisms for old people include, old people, seniors, senior citizens, older adults, the elderly, Old people often have limited regenerative abilities and are more susceptible to disease, syndromes, and sickness than younger adults. The organic process of ageing is called senescence, the study of the aging process is called gerontology. The elderly also face other social issues around retirement, loneliness, Old age is a social construct rather than a definite biological stage, and the chronological age denoted as old age varies culturally and historically. In 2011, the United Nations proposed a human rights convention that would specifically protect older persons, definitions of old age include official definitions, sub-group definitions, and four dimensions as follows. Old age comprises the part of life, the period of life after youth. At what age old age begins cannot be defined because it differs according to the context. Most developed-world countries have accepted the chronological age of 65 years as a definition of elderly or older person, the United Nations has agreed that 60+ years may be usually denoted as old age and this is the first attempt at an international definition of old age. However, for its study of old age in Africa, the World Health Organization set 50 as the beginning of old age. At the same time, the WHO recognized that the world often defines old age, not by years. Most developed Western countries set the age of 60 to 65 for retirement, being 60–65 years old is usually a requirement for becoming eligible for senior social programs. However, various countries and societies consider the onset of old age as anywhere from the mid-40s to the 70s, the definitions of old age continue to change especially as life expectancy in developed countries has risen to beyond 80 years old. Gerontologists have recognized the different conditions that people experience as they grow older within the years defined as old age. In developed countries, most people in their 60s and early 70s are still fit, active, however, after 75, they will become increasingly frail, a condition marked by serious mental and physical debilitation. Therefore, rather than lumping together all people who have defined as old. One study distinguishes the young old, the old. Another study’s sub-grouping is young-old, middle-old, and oldest-old, a third sub-grouping is “young old”, “old”, and old-old. Delineating sub-groups in the 65+ population enables an accurate portrayal of significant life changes

14.
Human fertilization
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Human fertilization is the union of a human egg and sperm, usually occurring in the ampulla of the fallopian tube. The result of union is the production of a zygote cell, or fertilized egg. Scientists discovered the dynamics of human fertilization in the nineteenth century, the process of fertilization involves a sperm fusing with an ovum. The most common sequence begins with ejaculation during copulation, follows with ovulation, various exceptions to this sequence are possible, including artificial insemination, in vitro fertilization, external ejaculation without copulation, or copulation shortly after ovulation. Upon encountering the secondary oocyte, the acrosome of the sperm produces enzymes which allow it to burrow through the outer coat of the egg. The sperm plasma then fuses with the plasma membrane, the sperm head disconnects from its flagellum. In vitro fertilization is a process by which egg cells are fertilized by sperm outside the womb, the sperm binds through the corona radiata, a layer of follicle cells on the outside of the secondary oocyte. Fertilization occurs when the nucleus of both a sperm and an egg fuse to form a cell, known as zygote. The successful fusion of forms a new organism. Where the spermatozoon is about to pierce, the yolk is drawn out into a conical elevation, once the spermatozoon has entered, the peripheral portion of the yolk changes into a membrane, the perivitelline membrane, which prevents the passage of additional spermatozoa. At the beginning of the process, the sperm undergoes a series of changes, after binding to the corona radiata the sperm reaches the zona pellucida, which is an extra-cellular matrix of glycoproteins. A special complementary molecule on the surface of the sperm binds to a ZP3 glycoprotein in the zona pellucida. This binding triggers the acrosome to burst, releasing enzymes that help the sperm get through the zona pellucida, some sperm cells consume their acrosome prematurely on the surface of the egg cell, facilitating the penetration by other sperm cells. As a population, sperm cells have on average 50% genome similarity so the premature acrosomal reactions aid fertilization by a member of the same cohort and it may be regarded as a mechanism of kin selection. Recent studies have shown that the egg is not passive during this process, once the sperm cells find their way past the zona pellucida, the cortical reaction occurs. Cortical granules inside the secondary oocyte fuse with the membrane of the cell. This prevents fertilization of an egg by more than one sperm, the cortical reaction and acrosome reaction are both essential to ensure that only one sperm will fertilize an egg. The oocyte now undergoes its second meiotic division producing the haploid ovum, the sperm nucleus then fuses with the ovum, enabling fusion of their genetic material

15.
Language acquisition
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Language acquisition is the process by which humans acquire the capacity to perceive and comprehend language, as well as to produce and use words and sentences to communicate. Language acquisition is one of the human traits, because non-humans do not communicate by using language. Language acquisition usually refers to first-language acquisition, which studies infants acquisition of their native language and this is distinguished from second-language acquisition, which deals with the acquisition of additional languages. The capacity to use language requires one to acquire a range of tools including phonology, morphology, syntax, semantics. Language can be vocalized as in speech, or manual as in sign, human language capacity is represented in the brain. Even though human language capacity is finite, one can say and understand a number of sentences. Evidence suggests that individual has three recursive mechanisms that allow sentences to go indeterminately. These three mechanisms are, relativization, complementation and coordination, some early observation-based ideas about language acquisition were proposed by Plato, who felt that word-meaning mapping in some form was innate. In a more modern context, empiricists, like Thomas Hobbes and John Locke, proponents of behaviorism argued that language may be learned through a form of operant conditioning. In B. F. Skinners Verbal Behaviour, he suggested that the use of a sign, such as a word or lexical unit, given a certain stimulus. Some empiricist theories of language include the statistical learning theory. Charles F. Hockett of language acquisition, relational frame theory, functionalist linguistics, social interactionist theory, Skinners behaviourist idea was strongly attacked by Noam Chomsky in a review article in 1959, calling it largely mythology and a serious delusion. Arguments against Skinners idea of language acquisition through operant conditioning include the fact that children often ignore language corrections from adults. Instead, children follow a pattern of using an irregular form of a word correctly, making errors later on. For example, a child may learn the word gave. Eventually, the child will go back to learning the correct word. The pattern is difficult to attribute to Skinners idea of operant conditioning as the way that children acquire language. Chomsky argued that if language were solely acquired through behavioral conditioning, children would not likely learn the use of a word

16.
Puberty
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Puberty is the process of physical changes through which a childs body matures into an adult body capable of sexual reproduction. It is initiated by signals from the brain to the gonads, the ovaries in a girl. In response to the signals, the gonads produce hormones that stimulate libido and the growth, function, and transformation of the brain, bones, muscle, blood, skin, hair, breasts, and sex organs. Physical growth—height and weight—accelerates in the first half of puberty and is completed when a body has been developed. Until the maturation of their capabilities, the pre-pubertal physical differences between boys and girls are the external sex organs. On average, girls begin puberty around ages 10–11, boys around ages 11–12, girls usually complete puberty around ages 15–17, while boys usually complete puberty around ages 16–17. In the 21st century, the age at which children, especially girls, reach puberty is lower compared to the 19th century. Puberty which starts earlier than usual is known as precocious puberty, Puberty which starts later than usual is known as delayed puberty. Two of the most significant differences between puberty in girls and puberty in boys are the age at which it begins, and the sex steroids involved, the testosterones. Although there is a range of normal ages, girls typically begin the process of puberty at age 10 or 11. Girls usually complete puberty by ages 15–17, while boys usually complete puberty by ages 16–17, girls attain reproductive maturity about four years after the first physical changes of puberty appear. In contrast, boys accelerate more slowly but continue to grow for about six years after the first visible pubertal changes, any increase in height beyond the post-pubertal age is uncommon. For boys, an androgen called testosterone is the sex hormone. While testosterone is produced, all changes are characterized as virilization. The conversion of testosterone to estradiol depends on the amount of body fat, the male growth spurt also begins later, accelerates more slowly, and lasts longer before the epiphyses fuse. Although boys are on average 2 centimetres shorter than girls before puberty begins, the hormone that dominates female development is an estrogen called estradiol. While estradiol promotes growth of the breasts and uterus, it is also the principal hormone driving the growth spurt and epiphyseal maturation. Estradiol levels rise earlier and reach higher levels in women than in men, the hormonal maturation of females is considerably more complicated than in boys

17.
Death
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Death is the cessation of all biological functions that sustain a living organism. Bodies of living organisms begin to decompose shortly after death, other concerns include fear of death, necrophobia, anxiety, sorrow, grief, emotional pain, depression, sympathy, compassion, solitude, or saudade. The potential for an afterlife is of concern for some humans, the word death comes from Old English deað, which in turn comes from Proto-Germanic *dauthuz. This comes from the Proto-Indo-European stem *dheu- meaning the Process, act, when a person has died, it is also said they have passed away, passed on, expired, or are gone, among numerous other socially accepted, religiously specific, slang, and irreverent terms. Bereft of life, the person is then a corpse, cadaver, a body, a set of remains, and when all flesh has rotted away. The terms carrion and carcass can also be used, though more often connote the remains of non-human animals. As a polite reference to a person, it has become common practice to use the participle form of decease, as in the deceased. The ashes left after a cremation are sometimes referred to by the neologism cremains, senescence refers to a scenario when a living being is able to survive all calamities, but eventually dies due to causes relating to old age. Almost all animals who survive external hazards to their biological functioning eventually die from biological aging, some organisms experience negligible senescence, even exhibiting biological immortality. These include the jellyfish Turritopsis dohrnii, the hydra, and the planarian, unnatural causes of death include suicide and homicide. From all causes, roughly 150,000 people die around the world each day, physiological death is now seen as a process, more than an event, conditions once considered indicative of death are now reversible. Where in the process a dividing line is drawn between life and death depends on factors beyond the presence or absence of vital signs, in general, clinical death is neither necessary nor sufficient for a determination of legal death. A patient with working heart and lungs determined to be dead can be pronounced legally dead without clinical death occurring. As scientific knowledge and medicine advance, formulating a precise definition of death becomes more difficult. The concept of death is a key to understanding of the phenomenon. There are many approaches to the concept. For example, brain death, as practiced in medical science, One of the challenges in defining death is in distinguishing it from life. As a point in time, death would seem to refer to the moment at which life ends, determining when death has occurred requires drawing precise conceptual boundaries between life and death

18.
Developmental psychology
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Developmental psychology is the scientific study of how and why human beings change over the course of their life. Originally concerned with infants and children, the field has expanded to include adolescence, adult development, aging, and this field examines change across three major dimensions, physical development, cognitive development, and socioemotional development. Developmental psychology examines the influences of nature and nurture on the process of human development, many researchers are interested in the interaction between personal characteristics, the individuals behavior and environmental factors, including social context and the built environment. Ongoing debates include biological essentialism vs. neuroplasticity and stages of development vs. dynamic systems of development, influential developmental psychologists from the 20th century include Urie Bronfenbrenner, Erik Erikson, Sigmund Freud, Jean Piaget, Barbara Rogoff, Esther Thelen, and Lev Vygotsky. Watson and Jean-Jacques Rousseau are typically cited as providing the foundations for modern developmental psychology, in the mid-18th century Jean Jacques Rousseau described three stages of development, infants, puer and adolescence in Emile, Or, On Education. Rousseaus ideas were taken up strongly by educators at the time, stanley Hall, who attempted to correlate ages of childhood with previous ages of mankind. James Mark Baldwin who wrote essays on topics that included Imitation, A Chapter in the Natural History of Consciousness and Mental Development in the Child, Baldwin was heavily involved in the theory of developmental psychology. Sigmund Freud, whose concepts were developmental, had a significant impact on public perceptions, Sigmund Freud believed that we all had a conscious, preconscious, and unconscious level. In the conscious we are aware of our mental process, the preconscious involves information that, though not currently in our thoughts, can be brought into consciousness. Lastly, the unconscious includes mental processes we are unaware of and he believed there is tension between the conscious and unconscious, because the conscious tries to hold back what the unconscious tries to express. To explain this he developed three personality structures, the id, ego, and superego, the id, the most primitive of the three, functions according to the pleasure principle, seek pleasure and avoid pain. The superego plays the critical and moralizing role, and the ego is the organized, based on this, he proposed five universal stages of development, that each are characterized by the erogenous zone that is the source of the childs psychosexual energy. The first is the stage, which occurs from birth to 12 months of age. During the oral stage the libido is centered in a babys mouth, the baby is able to suck. The second is the stage, from one to three years of age. During the anal stage, the child defecates from the anus, the third is the phallic stage, which occurs from three to five years of age. During the phallic stage, the child is aware of their sexual organs, the fourth is the latency stage, which occurs from age five until puberty. During the latency stage, the sexual interests are repressed

19.
Adolescence
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Adolescence is a transitional stage of physical and psychological development that generally occurs during the period from puberty to legal adulthood. Adolescence is usually associated with the years, but its physical, psychological or cultural expressions may begin earlier. For example, puberty now typically begins during preadolescence, particularly in females, physical growth, and cognitive development can extend into the early twenties. Thus age provides only a marker of adolescence, and scholars have found it difficult to agree upon a precise definition of adolescence. A thorough understanding of adolescence in society depends on information from various perspectives, including psychology, biology, history, sociology, education, and anthropology. Within all of these perspectives, adolescence is viewed as a period between childhood and adulthood, whose cultural purpose is the preparation of children for adult roles. It is a period of transitions involving education, training, employment and unemployment. The end of adolescence and the beginning of adulthood varies by country, Adolescence is usually accompanied by an increased independence allowed by the parents or legal guardians, including less supervision as compared to preadolescence. Major pubertal and biological changes include changes to the sex organs, height, weight, cognitive advances encompass both increment in knowledge and in the ability to think abstractly and to reason more effectively. The study of adolescent development often involves interdisciplinary collaborations, for example, researchers in neuroscience or bio-behavioral health might focus on pubertal changes in brain structure and its effects on cognition or social relations. Sociologists interested in adolescence might focus on the acquisition of social roles, developmental psychologists might focus on changes in relations with parents and peers as a function of school structure and pubertal status. Some scientists have questioned the universality of adolescence as a developmental phase, puberty is a period of several years in which rapid physical growth and psychological changes occur, culminating in sexual maturity. The average age of onset of puberty is at 11 for girls and 12 for boys, every persons individual timetable for puberty is influenced primarily by heredity, although environmental factors, such as diet and exercise, also exert some influences. These factors can contribute to precocious and delayed puberty. Some of the most significant parts of pubertal development involve distinctive physiological changes in height, weight, body composition. These changes are largely influenced by hormonal activity, puberty occurs through a long process and begins with a surge in hormone production, which in turn causes a number of physical changes. It is the stage of life characterized by the appearance and development of sex characteristics. This is triggered by the pituitary gland, which secretes a surge of hormonal agents into the blood stream, initiating a chain reaction to occur

20.
Positive Youth Development
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PYD is used in scientific literature and by practitioners who work with youth to refer to programs designed to optimize developmental progress. PYD differs from other approaches to youth in that it rejects an emphasis on trying to correct what is wrong with childrens behavior or development, programs and practitioners seek to empathize with, educate, and engage children in productive activities. While not particularly common in use yet, PYD has been used across the world to address social divisions, such as gender, Positive youth development originated from ecological systems theory to focus on the strengths of adolescence. It is also similar conceptually with the principles of positive psychology, the major catalyst for the development of positive youth development came as a response to the negative and punitive methods of the traditional youth development approach. Another aspect of the traditional approach lies in that many professionals, specific evidence of this problem-centered model is present across professional fields that deal with young people. Many connections can also be made to the current U. S. criminal justice model that favors punishment as opposed to prevention, encouraging the positive development of adolescents can help to lessen the likelihood of such problems arising by easing a healthy transition into adulthood. Or as solely a means of avoiding risky behaviors, rather than grounding its developmental approach in the presence of adversity, risk or challenge, a PYD approach considers the potential and capacity of each individual young person. Lerner and colleagues write, The goal of the youth development perspective is to promote positive outcomes. This idea is in contrast to a perspective that focuses on punishment, Positive youth development is both a vision, an ideology and a new vocabulary for engaging with youth development. Its tenets can be organized into the 5 Cs which are, competence, confidence, connection, character, when these 5 Cs are present, the 6th C of contribution is realized. This cultural sensitivity reflects the influence of Bronfenbrenners ecological systems theory, the University of Minnesotas Keys to Quality Youth Development summarizes eight key elements of programs that successfully promote youth development. Physical activity-based programs like Girls on the Run are being increasingly utilized around the world for their ability to encourage psychological, emotional, and social development for youth. Girls on the Run enhances this type of physical activity program by specifically targeting youth in an effort to reduce the gendered view of a male-dominated sports arena. Girls on the Run is a non-profit organization begun in 1996 that distributes a 12-week training program to help prepare for a 5k running competition. This particular program is available to 3rd through 5th grade female students throughout the United States. Another example of youth development principles being utilized to target youth gender inequities can be seen in that of a participatory diagramming approach in Kibera. This community development effort enabled participants to feel safe discussing their concerns regarding gender inequities in the community with the dominant male group and this approach also enabled youth to voice their needs and identify potential solutions related to topics like HIV/AIDS and family violence. Positive youth development can be used to combat negative stereotypes surrounding youth of minority groups in the U. S

21.
Adult development
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Adult development encompasses the changes that occur in biological, psychological, and interphonal domains of human life from the end of adolescence until the end of ones life. These changes may be gradual or rapid, and can reflect positive, negative, changes occur at the cellular level and are partially explained by biological theories of adult development and aging. Biological changes influence psychological and interpersonal/social developmental changes, which are described by stage theories of human development. Stage theories typically focus on “age-appropriate” developmental tasks to be achieved at each stage, erik Erikson and Carl Jung proposed stage theories of human development that encompass the entire life span, and emphasized the potential for positive change very late in life. The concept of adulthood has legal and socio-cultural definitions, the legal definition of an adult is a person who has reached the age at which they are considered responsible for their own actions, and therefore legally accountable for them. This is referred to as the age of majority, which is age 18 in most cultures and this may or may not coincide with the legal definition. Jeanne Louise Calment exemplifies successful aging as the longest living person and her long life can be attributed to her genetics and her active lifestyle and optimistic attitude. She enjoyed many hobbies and physical activities and believed that laughter contributed to her longevity and she poured olive oil on all of her food and skin, which she believed also contributed to her long life and youthful appearance. Changes in adulthood have been described by a number of theories and metatheories, Life span development is an overarching framework that considers individual development from conception to old age. The framework considers the accumulation of developmental gains and losses. According to this theory, life span development has multiple trajectories and causes, individual variation is a hallmark of this theory – not all individuals develop and age at the same rate and in the same manner. Erik Erikson developed stages of ego development that extended through childhood, adolescence and he was trained in psychoanalysis and was highly influenced by Freud, but unlike Freud, Erikson believed that social interaction is very important to the individuals psychosocial development. His stage theory consists of 8 stages in life from birth to old age, during each stage, one developmental task is dominant, but may be carried forward into later stages as well. According to Erikson, individuals may experience tension when advancing to new stages of development and it offers a standard method of examining the universal pattern of development. The archaic stage is characterized by consciousness, while the monarchic stage represents the beginning of logical. Youth, Maturing sexuality, growing consciousness, and a realization that the days of childhood are gone forever. People strive to gain independence, find a mate, and raise a family, middle Life, The realization that you will not live forever creates tension. If you desperately try to cling to youth, you will fail in the process of self-realization, Jung believed that in midlife, one confronts ones shadow

22.
Attachment theory
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Attachment theory is a psychological model that attempts to describe the dynamics of long-term and short-term interpersonal relationships between humans. However, attachment theory is not formulated as a theory of relationships. It addresses only a specific facet, how human beings respond within relationships when hurt, separated from loved ones, essentially all infants become attached if provided any caregiver, but there are individual differences in the quality of the relationships. Fathers or any other individuals, are likely to become principal attachment figures if they provide most of the child care. In the presence of a sensitive and responsive caregiver, the infant will use the caregiver as a base from which to explore. It should be recognized that even sensitive caregivers get it right only about 50 percent of the time and their communications are either out of synch, or mismatched. There are times when parents feel tired or distracted, the telephone rings or there is breakfast to prepare. In other words, attuned interactions rupture quite frequently, but the hallmark of a sensitive caregiver is that the ruptures are managed and repaired. Attachments between infants and caregivers form even if this caregiver is not sensitive and responsive in social interactions with them, infants cannot exit unpredictable or insensitive caregiving relationships. Instead they must manage themselves as best they can within such relationships, early patterns of attachment, in turn, shape — but do not determine — the individuals expectations in later relationships. Four different attachment classifications have been identified in children, secure attachment, anxious-ambivalent attachment, anxious-avoidant attachment, and disorganized attachment. Attachment theory has become the dominant theory used today in the study of infant and toddler behavior and in the fields of infant mental health, treatment of children, and related fields. Secure attachment is when children feel they can rely on their caregivers to attend to their needs of proximity, emotional support and it is considered to be the best attachment style. Anxious-ambivalent attachment is when the infant feels separation anxiety when separated from the caregiver, anxious-avoidant attachment is when the infant avoids their parents. Disorganized attachment is when there is a lack of attachment behavior, in the 1980s, the theory was extended to attachment in adults. Attachment applies to adults when adults feel close attachment to their parents, within attachment theory, attachment means a biological instinct in which proximity to an attachment figure is sought when the child senses or perceives threat or discomfort. Attachment behaviour anticipates a response by the attachment figure which will remove threat or discomfort. Such bonds may be reciprocal between two adults, but between a child and a caregiver these bonds are based on the childs need for safety, security and protection, paramount in infancy, in the most complex organisms, instinctive behaviors may be goal-corrected with continual on-course adjustments

23.
Ecological systems theory
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Ecological systems theory, also called development in context or human ecology theory, identifies five environmental systems with which an individual interacts. This theory provides the framework from which community psychologists study the relationships with individuals contexts within communities, Ecological systems theory was developed by Urie Bronfenbrenner. Microsystem, Refers to the institutions and groups that most immediately and directly impact the development including, family, school, religious institutions, neighborhood. For example, a parents or childs experience at home may be influenced by the other parents experiences at work, the parent might receive a promotion that requires more travel, which might increase conflict with the other parent and change patterns of interaction with the child. Macrosystem, Describes the culture in which individuals live, cultural contexts include developing and industrialized countries, socioeconomic status, poverty, and ethnicity. A child, his or her parent, his or her school, members of a cultural group share a common identity, heritage, and values. The macrosystem evolves over time, because each generation may change the macrosystem. Chronosystem, The patterning of environmental events and transitions over the life course, for example, divorces are one transition. Researchers have found that the effects of divorce on children often peak in the first year after the divorce. By two years after the divorce, family interaction is less chaotic and more stable, an example of sociohistorical circumstances is the increase in opportunities for women to pursue a career during the last thirty years. The persons own biology may be considered part of the microsystem, per this theoretical construction, each system contains roles, norms and rules which may shape psychological development. For example, an inner-city family faces many challenges which an affluent family in a gated community does not, the inner-city family is more likely to experience environmental hardships, like crime and squalor. On the other hand, the family is more likely to lack the nurturing support of extended family. Bronfenbrenner has identified Soviet developmental psychologist Lev Vygotsky and German-born psychologist Kurt Lewin as important influences on his theory, there are many different theories related to human development. The ecological theory emphasizes environmental factors as playing the role to development. Bioecological model Ecosystem Ecosystem ecology Systems ecology Systems psychology Theoretical ecology Urie Bronfenbrenner, the Ecology of Human Development, Experiments by Nature and Design. ISBN 0-674-22457-4 Dede Paquette & John Ryan, Bronfenbrenner’s Ecological Systems Theory Woodside, Arch G. Caldwell, Marylouise, Spurr, Ray. Advancing Ecological Systems Theory in Lifestyle, Leisure, and Travel Research, marlowe E. Trance, Kerstin O. Flores

24.
Psychosexual development
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Each stage – the oral, the anal, the phallic, the latent, and the genital – is characterized by the erogenous zone that is the source of the libidinal drive. He argued that adult neurosis often is rooted in childhood sexuality, sexual infantilism, in pursuing and satisfying his or her libido, the child might experience failure and thus might associate anxiety with the given erogenous zone. e. The tendency to place objects in the mouth, the id dominates, because neither the ego nor the super ego is yet fully developed, and, since the infant has no personality, every action is based upon the pleasure principle. Nonetheless, the ego is forming during the oral stage, two factors contribute to its formation, in developing a body image, he or she is discrete from the external world. Weaning is the key experience in the oral stage of psychosexual development. In the case of too little gratification, the infant might become passive upon learning that gratification is not forthcoming, the style of parenting influences the resolution of the id–ego conflict, which can be either gradual and psychologically uneventful, or which can be sudden and psychologically traumatic. If the child obeys the id, and the yield, he or she might develop a self-indulgent personality characterized by personal slovenliness. If the parents respond to that, the child must comply, but might develop a sense of self, because it was the parents will, and not the childs ego. The third stage of development is the phallic stage, spanning the ages of three to six years, wherein the childs genitalia are his or her primary erogenous zone. In the phallic stage, a boys decisive psychosexual experience is the Oedipus complex and this psychological complex derives from the 5th-century BC Greek mythologic character Oedipus, who unwittingly killed his father, Laius, and sexually possessed his mother, Jocasta. Analogously, in the stage, a girls decisive psychosexual experience is the Electra complex. The boy focuses his libido upon his mother, and focuses jealousy, Electra, Whereas boys develop castration anxiety, girls develop penis envy that is rooted in anatomic fact, without a penis, she cannot sexually possess mother, as the infantile id demands. As a result, the girl redirects her desire for sexual union upon father, thus, moreover, after the phallic stage, the girls psychosexual development includes transferring her primary erogenous zone from the infantile clitoris to the adult vagina. Freud thus considered a girls Oedipal conflict to be more intense than that of a boy, resulting, potentially. Psychologic defense, In both sexes, defense mechanisms provide transitory resolutions of the conflict between the drives of the Id and the drives of the Ego. The first defense mechanism is repression, the blocking of memories, emotional impulses, in a boy, a phallic-stage fixation might lead him to become an aggressive, over-ambitious, vain man. The genital stage affords the person the ability to confront and resolve his or her remaining psychosexual childhood conflicts, as in the phallic stage, the genital stage is centered upon the genitalia, but the sexuality is consensual and adult, rather than solitary and infantile. Hence, the stage proved controversial, for being based upon clinical observations of the Oedipus complex

25.
Piaget's theory of cognitive development
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Piagets theory of cognitive development is a comprehensive theory about the nature and development of human intelligence. It was first created by the Swiss developmental psychologist Jean Piaget, the theory deals with the nature of knowledge itself and how humans gradually come to acquire, construct, and use it. Piagets theory is known as a developmental stage theory. To Piaget, cognitive development was a reorganization of mental processes resulting from biological maturation. Moreover, Piaget claimed that development is at the center of the human organism. Piagets earlier work received the greatest attention, child-centered classrooms and open education are direct applications of Piagets views. Despite its huge success, Piagets theory has some limitations that Piaget recognized himself, for example, Piaget noted that reality is a dynamic system of continuous change and, as such, is defined in reference to the two conditions that define dynamic systems. Specifically, he argued that reality involves transformations and states, transformations refer to all manners of changes that a thing or person can undergo. States refer to the conditions or the appearances in which things or persons can be found between transformations, for example, there might be changes in shape or form, in size, or in placement or location in space and time. Thus, Piaget argued, if human intelligence is to be adaptive, operative intelligence is the active aspect of intelligence. It involves all actions, overt or covert, undertaken in order to follow, recover, figurative intelligence is the more or less static aspect of intelligence, involving all means of representation used to retain in mind the states that intervene between transformations. That is, it involves perception, imitation, mental imagery, drawing, at any time, operative intelligence frames how the world is understood and it changes if understanding is not successful. Piaget stated that this process of understanding and change involves two basic functions, assimilation and accommodation, through his study of the field of education, Piaget focused on two processes, which he named assimilation and accommodation. To Piaget, assimilation meant integrating external elements into structures of lives or environments, assimilation is how humans perceive and adapt to new information. It is the process of fitting new information into pre-existing cognitive schemas, assimilation in which new experiences are reinterpreted to fit into, or assimilate with, old ideas. It occurs when humans are faced with new or unfamiliar information, in contrast, accommodation is the process of taking new information in ones environment and altering pre-existing schemas in order to fit in the new information. This happens when the schema does not work, and needs to be changed to deal with a new object or situation. Accommodation is imperative because it is how people will continue to interpret new concepts, schemas, frameworks, Piagets understanding was that assimilation and accommodation cannot exist without the other

26.
Latin language
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Latin is a classical language belonging to the Italic branch of the Indo-European languages. The Latin alphabet is derived from the Etruscan and Greek alphabets, Latin was originally spoken in Latium, in the Italian Peninsula. Through the power of the Roman Republic, it became the dominant language, Vulgar Latin developed into the Romance languages, such as Italian, Portuguese, Spanish, French, and Romanian. Latin, Italian and French have contributed many words to the English language, Latin and Ancient Greek roots are used in theology, biology, and medicine. By the late Roman Republic, Old Latin had been standardised into Classical Latin, Vulgar Latin was the colloquial form spoken during the same time and attested in inscriptions and the works of comic playwrights like Plautus and Terence. Late Latin is the language from the 3rd century. Later, Early Modern Latin and Modern Latin evolved, Latin was used as the language of international communication, scholarship, and science until well into the 18th century, when it began to be supplanted by vernaculars. Ecclesiastical Latin remains the language of the Holy See and the Roman Rite of the Catholic Church. Today, many students, scholars and members of the Catholic clergy speak Latin fluently and it is taught in primary, secondary and postsecondary educational institutions around the world. The language has been passed down through various forms, some inscriptions have been published in an internationally agreed, monumental, multivolume series, the Corpus Inscriptionum Latinarum. Authors and publishers vary, but the format is about the same, volumes detailing inscriptions with a critical apparatus stating the provenance, the reading and interpretation of these inscriptions is the subject matter of the field of epigraphy. The works of several hundred ancient authors who wrote in Latin have survived in whole or in part and they are in part the subject matter of the field of classics. The Cat in the Hat, and a book of fairy tales, additional resources include phrasebooks and resources for rendering everyday phrases and concepts into Latin, such as Meissners Latin Phrasebook. The Latin influence in English has been significant at all stages of its insular development. From the 16th to the 18th centuries, English writers cobbled together huge numbers of new words from Latin and Greek words, dubbed inkhorn terms, as if they had spilled from a pot of ink. Many of these words were used once by the author and then forgotten, many of the most common polysyllabic English words are of Latin origin through the medium of Old French. Romance words make respectively 59%, 20% and 14% of English, German and those figures can rise dramatically when only non-compound and non-derived words are included. Accordingly, Romance words make roughly 35% of the vocabulary of Dutch, Roman engineering had the same effect on scientific terminology as a whole

27.
Developmental biology
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Developmental biology is the study of the process by which animals and plants grow and develop. Developmental biology also encompasses the biology of regeneration, asexual reproduction and metamorphosis and in the growth, regional specification refers to the processes that create spatial pattern in a ball or sheet of initially similar cells. This generally involves the action of cytoplasmic determinants, located within parts of the fertilized egg, the early stages of regional specification do not generate functional differentiated cells, but cell populations committed to develop to a specific region or part of the organism. These are defined by the expression of combinations of transcription factors. Morphogenesis relates to the formation of three-dimensional shape and it mainly involves the orchestrated movements of cell sheets and of individual cells. Morphogenesis is important for creating the three layers of the early embryo and for building up complex structures during organ development. Cell differentiation relates specifically to the formation of cell types such as nerve, muscle. Differentiated cells contain large amounts of proteins associated with the cell function. Growth involves both an increase in size, and also the differential growth of parts which contributes to morphogenesis. Growth mostly occurs through cell division but also changes of cell size. The control of timing of events and the integration of the processes with one another is the least well understood area of the subject. It remains unclear whether animal embryos contain a master clock mechanism or not, the development of plants involves similar processes to that of animals. However plant cells are mostly immotile so morphogenesis is achieved by differential growth, also, the inductive signals and the genes involved in plant development are different from those that control animal development. Cell differentiation is the process whereby different functional cell types arise in development, for example, neurons, muscle fibers and hepatocytes are well known types of differentiated cell. The genes encoding these proteins are highly active, for example, NeuroD is a key transcription factor for neuronal differentiation, myogenin for muscle differentiation, and HNF4 for hepatocyte differentiation. Cell differentiation is usually the final stage of development, preceded by several states of commitment which are not visibly differentiated, a single tissue, formed from a single type of progenitor cell or stem cell, often consists of several differentiated cell types. Control of their formation involves a process of inhibition, based on the properties of the Notch signaling pathway. For example, in the plate of the embryo this system operates to generate a population of neuronal precursor cells in which NeuroD is highly expressed

28.
Psychological
–
Psychology is the science of behavior and mind, embracing all aspects of conscious and unconscious experience as well as thought. It is a discipline and a social science which seeks to understand individuals and groups by establishing general principles. In this field, a professional practitioner or researcher is called a psychologist and can be classified as a social, behavioral, Psychologists explore behavior and mental processes, including perception, cognition, attention, emotion, intelligence, phenomenology, motivation, brain functioning, and personality. This extends to interaction between people, such as relationships, including psychological resilience, family resilience, and other areas. Psychologists of diverse orientations also consider the unconscious mind, Psychologists employ empirical methods to infer causal and correlational relationships between psychosocial variables. Psychology has been described as a hub science, with psychological findings linking to research and perspectives from the sciences, natural sciences, medicine, humanities. By many accounts psychology ultimately aims to benefit society, the majority of psychologists are involved in some kind of therapeutic role, practicing in clinical, counseling, or school settings. Many do scientific research on a range of topics related to mental processes and behavior. The word psychology derives from Greek roots meaning study of the psyche, the Latin word psychologia was first used by the Croatian humanist and Latinist Marko Marulić in his book, Psichiologia de ratione animae humanae in the late 15th century or early 16th century. In 1890, William James defined psychology as the science of mental life and this definition enjoyed widespread currency for decades. Also since James defined it, the more strongly connotes techniques of scientific experimentation. Folk psychology refers to the understanding of people, as contrasted with that of psychology professionals. The ancient civilizations of Egypt, Greece, China, India, historians note that Greek philosophers, including Thales, Plato, and Aristotle, addressed the workings of the mind. As early as the 4th century BC, Greek physician Hippocrates theorized that mental disorders had physical rather than supernatural causes, in China, psychological understanding grew from the philosophical works of Laozi and Confucius, and later from the doctrines of Buddhism. This body of knowledge involves insights drawn from introspection and observation and it frames the universe as a division of, and interaction between, physical reality and mental reality, with an emphasis on purifying the mind in order to increase virtue and power. Chinese scholarship focused on the advanced in the Qing Dynasty with the work of Western-educated Fang Yizhi, Liu Zhi. Distinctions in types of awareness appear in the ancient thought of India, a central idea of the Upanishads is the distinction between a persons transient mundane self and their eternal unchanging soul. Divergent Hindu doctrines, and Buddhism, have challenged this hierarchy of selves, yoga is a range of techniques used in pursuit of this goal

29.
Age of majority
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The age of majority is the threshold of adulthood as recognized or declared in law. Most countries set the age of majority at 18, the word majority here refers to having greater years and being of full age as opposed to minority, the state of being a minor. The law in a jurisdiction may not actually use the term age of majority. The term typically refers to a collection of laws bestowing the status of adulthood, the age of majority does not necessarily correspond to the mental or physical maturity of an individual. Age of majority can be confused with the concept of the age of license. As a legal term of art, license means permission, thus, an age of license is an age at which one has legal permission from government to do something. The age of majority, on the hand, is legal recognition that one has grown into an adult. Many ages of license are correlated to the age of majority, one need not have attained the age of majority to have permission to exercise certain rights and responsibilities. Some ages of license are actually higher than the age of majority, for example, the age of license to purchase alcoholic beverages is 21 in all U. S. states. Another example is the age, which prior to the 1970s was 21. In the Republic of Ireland the age of majority is 18, also, in Portugal the age of majority is 18, but one must be at least 25 years of age to run for public office. A child who is legally emancipated by a court of competent jurisdiction automatically attains to their maturity upon the signing of the court order, only emancipation confers the status of maturity before a person has actually reached the age of majority. In almost all places, minors who are married are automatically emancipated, some places also do the same for minors who are in the armed forces or who have a certain degree or diploma. In the United States, all states have some form of emancipation of minors, judaism,13 years of age for males and 12 years of age for females, such persons are considered adults Roman Catholic Church,18 years of age

My Chemical Romance
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My Chemical Romance was an American rock band from New Jersey, active from 2001 to 2013. The bands best-known lineup consisted of lead vocalist Gerard Way, guitarists Ray Toro and Frank Iero, bassist Mikey Way and drummer Bob Bryar. Founded by Gerard, Mikey, Toro, Matt Pelissier, and later joined by Iero and they signed with Reprise Records the nex

3.
My Chemical Romance on tour, wearing the clothes of The Black Parade.

4.
Most of the concerts of The Black Parade World Tour involved use of pyrotechnics, especially during "Mama" and " Famous Last Words ".

Teenagers (song)
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Teenagers is the fourth and final single and the eleventh track from My Chemical Romances third studio album, The Black Parade. It is the third United States single from the album, but it is the single released in the United Kingdom. This song is the eleventh overall single. The song was released to radio on May 15,2007, despite charting at #67 on

1.
"Teenagers"

2.
Promotional cover

Teenage (film)
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Teenage is a 2013 documentary film directed by Matt Wolf and based on Jon Savages book Teenage, The Creation of Youth Culture. In the documentary, Wolf attempts to bring to life the prehistory of youth culture which preceded and evolved into the concept of culture in the 1950s. The film had its premiere at the Tribeca Film Festival on April 20,2013

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Film poster

Oslo
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Oslo is the capital and the most populous city in Norway. It constitutes both a county and a municipality, founded in the year 1040, and established as a kaupstad or trading place in 1048 by Harald Hardrada, the city was elevated to a bishopric in 1070 and a capital under Haakon V of Norway around 1300. Personal unions with Denmark from 1397 to 152

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From upper left: Rising skyline over Bjørvika, Royal Palace, Akershus Castle, sunset over the Oslofjord, Stortinget, Oslo Opera House

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Det Kongelige Slott (The Royal Palace) is the home of the Royal Family.

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Port of Christiania anno 1800 Aquatint by John William Edy

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The seal of Haakon V Magnusson, the King who made Oslo the capital of Norway

Human development (biology)
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Human development is the process of growing to maturity. In biological terms, this entails growth from a zygote to an adult human being. Fertilization occurs when the sperm enters the ovums membrane. The genetical material of the sperm and egg that combine to form a cell, called a zygote. The germinal stage refers to the time from fertilization, th

1.
"Developmental" redirects here. For other uses, see Development.

Human embryogenesis
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Human embryogenesis is the process of cell division and cellular differentiation of the embryo that occurs during the early stages of development. In biological terms, human development entails growth from a zygote to an adult human being. Fertilisation occurs when the cell successfully enters and fuses with an egg cell. The genetic material of the

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8-cell embryo, at 3 days

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Histogenesis of the three germ layers

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Embryo attached to placenta in amniotic cavity

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This article is about Human embryogenesis. For Embryogenesis in general, see Embryogenesis.

Fetus
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A fetus is a stage in the prenatal development of viviparous organisms. In human development, a fetus or foetus is a human between the embryonic state and birth. The fetal stage of development tends to be taken as beginning at the age of eleven weeks. In biological terms, however, prenatal development is a continuum, the use of the term fetus gener

1.
A human fetus, attached to placenta, at around twelve weeks after fertilization. Until around nine weeks after fertilization, this prenatal human would have been described as an embryo.

Infant
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An infant is the more formal or specialised synonym for baby, the very young offspring of a human or other animal. A newborn is, in use, an infant who is only hours, days. In medical contexts, newborn or neonate refers to an infant in the first 28 days after birth, the term applies to premature, full term, and postmature infants, before birth, the

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Eight-month-old twin sisters

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Eight months old infant; as a common feature eyes are usually larger compared to the face.

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A crying newborn, a few days after birth

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A newborn baby in Indonesia, with umbilical cord ready to be clamped

Toddler
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A toddler is a child 12 to 36 months old. The toddler years are a time of great cognitive, emotional and social development, the word is derived from to toddle, which means to walk unsteadily, like a child of this age. Toddler development can be broken down into a number of interrelated areas, there is reasonable consensus about what these include,

Preadolescence
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Preadolescence, also known as pre-teen or tween, is a stage of human development following early childhood and preceding adolescence. It commonly ends with the beginning of puberty, but may also be defined as ending with the start of the teenage years, for example, dictionary definitions generally designate it as 10–13 years. Preadolescence can bri

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Approximate outline of development periods in child development. Preadolescence and preteen marked at center left.

Adult
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Biologically, an adult is a human or other organism that has reached sexual maturity. In human context, the term adult additionally has meanings associated with social and legal concepts, in contrast to a minor, a legal adult is a person who has attained the age of majority and is therefore regarded as independent, self-sufficient, and responsible.

1.
A group of adult people.

Middle age
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In the history of Europe, the Middle Ages or Medieval Period lasted from the 5th to the 15th century. It began with the fall of the Western Roman Empire and merged into the Renaissance, the Middle Ages is the middle period of the three traditional divisions of Western history, classical antiquity, the medieval period, and the modern period. The med

1.
The Cross of Mathilde, a crux gemmata made for Mathilde, Abbess of Essen (973–1011), who is shown kneeling before the Virgin and Child in the enamel plaque. The body of Christ is slightly later. Probably made in Cologne or Essen, the cross demonstrates several medieval techniques: cast figurative sculpture, filigree, enamelling, gem polishing and setting, and the reuse of Classical cameos and engraved gems.

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A late Roman statue depicting the four Tetrarchs, now in Venice

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Coin of Theodoric

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Mosaic showing Justinian with the bishop of Ravenna, bodyguards, and courtiers

Old age
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Old age refers to ages nearing or surpassing the life expectancy of human beings, and is thus the end of the human life cycle. Terms and euphemisms for old people include, old people, seniors, senior citizens, older adults, the elderly, Old people often have limited regenerative abilities and are more susceptible to disease, syndromes, and sickness

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An image of an elderly man being guided by a young child accompanies William Blake 's poem London. This image is a digital repercussion of his hand-painted 1826 print from Copy AA of Songs of Innocence and Experience. The item is currently in the collection of the Fitzwilliam Museum.

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An elderly Somali woman.

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An elderly Khmer woman.

Human fertilization
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Human fertilization is the union of a human egg and sperm, usually occurring in the ampulla of the fallopian tube. The result of union is the production of a zygote cell, or fertilized egg. Scientists discovered the dynamics of human fertilization in the nineteenth century, the process of fertilization involves a sperm fusing with an ovum. The most

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The acrosome reaction for a sea urchin, a similar process. Note that the picture shows several stages of one and the same spermatozoon - only one penetrates the ovum

Language acquisition
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Language acquisition is the process by which humans acquire the capacity to perceive and comprehend language, as well as to produce and use words and sentences to communicate. Language acquisition is one of the human traits, because non-humans do not communicate by using language. Language acquisition usually refers to first-language acquisition, w

1.
Learning box for language acquisition

Puberty
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Puberty is the process of physical changes through which a childs body matures into an adult body capable of sexual reproduction. It is initiated by signals from the brain to the gonads, the ovaries in a girl. In response to the signals, the gonads produce hormones that stimulate libido and the growth, function, and transformation of the brain, bon

Death
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Death is the cessation of all biological functions that sustain a living organism. Bodies of living organisms begin to decompose shortly after death, other concerns include fear of death, necrophobia, anxiety, sorrow, grief, emotional pain, depression, sympathy, compassion, solitude, or saudade. The potential for an afterlife is of concern for some

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A human skull, widely used as a symbol of death and decomposition

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A dead Eurasian magpie

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A dead rat

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A flower, a skull and an hourglass stand for Life, Death and Time in this 17th-century painting by Philippe de Champaigne

Developmental psychology
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Developmental psychology is the scientific study of how and why human beings change over the course of their life. Originally concerned with infants and children, the field has expanded to include adolescence, adult development, aging, and this field examines change across three major dimensions, physical development, cognitive development, and soc

1.
Special methods are used in the psychological study of infants.

Adolescence
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Adolescence is a transitional stage of physical and psychological development that generally occurs during the period from puberty to legal adulthood. Adolescence is usually associated with the years, but its physical, psychological or cultural expressions may begin earlier. For example, puberty now typically begins during preadolescence, particula

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Two adolescents listening to music

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Adolescents of diverse backgrounds in Oslo

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Upper body of a teenage boy. The structure has changed to resemble an adult form.

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G. Stanley Hall

Positive Youth Development
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PYD is used in scientific literature and by practitioners who work with youth to refer to programs designed to optimize developmental progress. PYD differs from other approaches to youth in that it rejects an emphasis on trying to correct what is wrong with childrens behavior or development, programs and practitioners seek to empathize with, educat

1.
Youth participating in Under Pressure, a North American graffiti festival utilizing Positive Youth Development principles.

Adult development
–
Adult development encompasses the changes that occur in biological, psychological, and interphonal domains of human life from the end of adolescence until the end of ones life. These changes may be gradual or rapid, and can reflect positive, negative, changes occur at the cellular level and are partially explained by biological theories of adult de

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An elderly couple exhibiting typical signs of physical aging.

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Erik Erikson, psychosocial development theorist.

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Older adults are often at higher risk for disorders such as depression.

Attachment theory
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Attachment theory is a psychological model that attempts to describe the dynamics of long-term and short-term interpersonal relationships between humans. However, attachment theory is not formulated as a theory of relationships. It addresses only a specific facet, how human beings respond within relationships when hurt, separated from loved ones, e

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For infants and toddlers, the "set-goal" of the attachment behavioral system is to maintain or achieve proximity to attachment figures, usually the parents.

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The attachment system serves to achieve or maintain proximity to the attachment figure. In close physical proximity this system is not activitated, and the infant can direct its attention to the outside world.

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Insecure attachment patterns can compromise exploration and the achievement of self-confidence. A securely attached baby is free to concentrate on her or his environment.

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Early experiences with caregivers gradually give rise to a system of thoughts, memories, beliefs, expectations, emotions, and behaviours about the self and others.

Ecological systems theory
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Ecological systems theory, also called development in context or human ecology theory, identifies five environmental systems with which an individual interacts. This theory provides the framework from which community psychologists study the relationships with individuals contexts within communities, Ecological systems theory was developed by Urie B

1.
Bronfenbrenner's ecological systems theory

Psychosexual development
–
Each stage – the oral, the anal, the phallic, the latent, and the genital – is characterized by the erogenous zone that is the source of the libidinal drive. He argued that adult neurosis often is rooted in childhood sexuality, sexual infantilism, in pursuing and satisfying his or her libido, the child might experience failure and thus might associ

Piaget's theory of cognitive development
–
Piagets theory of cognitive development is a comprehensive theory about the nature and development of human intelligence. It was first created by the Swiss developmental psychologist Jean Piaget, the theory deals with the nature of knowledge itself and how humans gradually come to acquire, construct, and use it. Piagets theory is known as a develop

Latin language
–
Latin is a classical language belonging to the Italic branch of the Indo-European languages. The Latin alphabet is derived from the Etruscan and Greek alphabets, Latin was originally spoken in Latium, in the Italian Peninsula. Through the power of the Roman Republic, it became the dominant language, Vulgar Latin developed into the Romance languages

1.
Latin inscription, in the Colosseum

2.
Julius Caesar 's Commentarii de Bello Gallico is one of the most famous classical Latin texts of the Golden Age of Latin. The unvarnished, journalistic style of this patrician general has long been taught as a model of the urbane Latin officially spoken and written in the floruit of the Roman republic.

Developmental biology
–
Developmental biology is the study of the process by which animals and plants grow and develop. Developmental biology also encompasses the biology of regeneration, asexual reproduction and metamorphosis and in the growth, regional specification refers to the processes that create spatial pattern in a ball or sheet of initially similar cells. This g

1.
Views of a Fetus in the Womb, Leonardo da Vinci, c. 1510 - 1512. The subject of prenatal development is a major subset of developmental biology.

Psychological
–
Psychology is the science of behavior and mind, embracing all aspects of conscious and unconscious experience as well as thought. It is a discipline and a social science which seeks to understand individuals and groups by establishing general principles. In this field, a professional practitioner or researcher is called a psychologist and can be cl

1.
Wilhelm Wundt (seated) with colleagues in his psychological laboratory, the first of its kind.

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MRI depicting the human brain. The arrow indicates the position of the hypothalamus.

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Social psychology studies the nature and causes of social behavior.

Age of majority
–
The age of majority is the threshold of adulthood as recognized or declared in law. Most countries set the age of majority at 18, the word majority here refers to having greater years and being of full age as opposed to minority, the state of being a minor. The law in a jurisdiction may not actually use the term age of majority. The term typically

1.
The 1960s Civil Rights Movement in the United States is an example of a social movement. Pictured are marchers at the Lincoln Memorial during the March on Washington for Jobs and Freedom in Washington, D.C. on August 28, 1963.

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Troops of the Eight-Nation Alliance in 1900, shows British and American soldiers significantly taller than some soldiers of the world. Left-to-right: Britain, United States, Australian colonial, British India, Germany, France, Russia, Italy, Japan.

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Photo of the Jean Piaget Foundation with Pierre Bovet (1878–1965) first row (with large beard) and Jean Piaget (1896–1980) first row (on the right, with glasses) in front of the Rousseau Institute (Geneva), 1925

3.
These fMRI images are from a study showing parts of the brain lighting up on seeing houses and other parts on seeing faces. The 'r' values are correlations, with higher positive or negative values indicating a better match.